[XERCESC-2227] Memleak fixes in ContentSpecNode and ComplexTypeInfo classes

XERCESC-2208: XMLSize_t size_t revert

ComplexTypeInfo::expandContentModel(): restore use of retNode as in original code (this is equivalent)

XERCESC-2208: Use cstdint and standard integer types

XERCESC-2226: Update minimum CMake version to 3.12

* Required for CURL imported target usage in XERCESC-2225
* Drop old cmake_policy settings which are now the default behaviour

XERCESC-2225: Link to installed CMake targets of CURL

[XERCESC-2224] DFAContentModel::checkUniqueParticleAttribution (): speed enhancement

The complexity of this method is roughly O(n^3). Fuzzers can generate
schemas with n = several thousands. The test fTransTable[i][j] == XMLContentModel::gInvalidTrans
is independant of the k loop, and can thus being moved at a upper level
to improve runtime.

[XERCESC-2223] SAX2XMLReaderImpl::error(): use exception memory manager, …

SAX2XMLReaderImpl::error(): use exception memory manager, otherwise regular memory manager might fail to fully allocate the strings in the exception and cause memory leaks

[XERCESC-2222] DFAContentModel::checkUniqueParticleAttribution(): fix memory leak

If a memory allocation of conflictTable[] fails, or later in the
function, the array is not freed.
Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=38533

Fix -Wmemset-transposed-args warnings of clang++

XERCESC-2221: InMemMsgLoader::loadMsg(): fix memory leak when transcoding fails.

Just like how it was done for ICU

Fixes:
xercesc/util/XMLChTranscoder.cpp:73:23: warning: setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments? [-Wmemset-transposed-args]
    memset(charSizes, sizeof(XMLCh), countToDo);
                      ^
xercesc/util/XMLChTranscoder.cpp:73:23: note: cast the second argument to 'int' to silence

and

xercesc/util/XMLUTF16Transcoder.cpp:114:23: warning: setting buffer to a 'sizeof' expression; did you mean to transpose the last two arguments? [-Wmemset-transposed-args]
    memset(charSizes, sizeof(UTF16Ch), countToDo);
                      ^
xercesc/util/XMLUTF16Transcoder.cpp:114:23: note: cast the second argument to 'int' to silence
1 warning generated.

Seen with the IconvGNU transcoder when parsing "<aaa.xsdopengis.net/gml\x96".
The reason is that XMLString::transcode(repText2, manager) throws a TranscodingException
which causes the tmp1 string to leak.

```
0 0x8791409 in operator new(unsigned int) /src/llvm-project/compiler-rt/lib/asan/asan_new_delete.cpp:99:3
1 0xbd147f7 in xercesc_4_0::MemoryManagerImpl::allocate(unsigned int) gdal/xerces-c/src/xercesc/internal/MemoryManagerImpl.cpp:40:18
2 0xbe8c73e in xercesc_4_0::IconvGNULCPTranscoder::transcode(char const*, xercesc_4_0::MemoryManager*) gdal/xerces-c/src/xercesc/util/Transcoders/IconvGNU/IconvGNUTransService.cpp:870:32
3 0xbc22ca2 in xercesc_4_0::XMLString::transcode(char const*, xercesc_4_0::MemoryManager*) gdal/xerces-c/src/xercesc/util/XMLString.cpp:621:25
4 0xbe8f4ad in xercesc_4_0::InMemMsgLoader::loadMsg(unsigned int, char16_t*, unsigned int, char const*, char const*, char const*, char const*, xercesc_4_0::MemoryManager*) gdal/xerces-c/src/xercesc/util/MsgLoaders/InMemory/InMemMsgLoader.cpp:157:16
5 0xbc20175 in xercesc_4_0::XMLException::loadExceptText(xercesc_4_0::XMLExcepts::Codes, char const*, char const*, char const*, char const*) gdal/xerces-c/src/xercesc/util/XMLException.cpp:241:23
6 0xbc48bee in xercesc_4_0::UTFDataFormatException::UTFDataFormatException(char const*, unsigned long long, xercesc_4_0::XMLExcepts::Codes, char const*, char const*, char const*, char const*, xercesc_4_0::MemoryManager*) gdal/xerces-c/src/xercesc/util/UTFDataFormatException.hpp:31:1
7 0xbc4824e in xercesc_4_0::XMLUTF8Transcoder::transcodeFrom(unsigned char const*, unsigned int, char16_t*, unsigned int, unsigned int&, unsigned char*) gdal/xerces-c/src/xercesc/util/XMLUTF8Transcoder.cpp:182:13
8 0xbd27d7e in xercesc_4_0::XMLReader::xcodeMoreChars(char16_t*, unsigned char*, unsigned int) gdal/xerces-c/src/xercesc/internal/XMLReader.cpp:1926:34
9 0xbd271dd in xercesc_4_0::XMLReader::refreshCharBuffer() gdal/xerces-c/src/xercesc/internal/XMLReader.cpp:571:19
10 0xbd15c63 in xercesc_4_0::XMLReader::peekNextChar(char16_t&) gdal/xerces-c/src/xercesc/internal/XMLReader.hpp:767:14
11 0xbd15aaf in xercesc_4_0::ReaderMgr::peekNextChar() gdal/xerces-c/src/xercesc/internal/ReaderMgr.cpp:158:21
12 0xbd328da in xercesc_4_0::XMLScanner::scanProlog() gdal/xerces-c/src/xercesc/internal/XMLScanner.cpp:1241:45
13 0xbd31ef4 in xercesc_4_0::XMLScanner::scanFirst(xercesc_4_0::InputSource const&, xercesc_4_0::XMLPScanToken&) gdal/xerces-c/src/xercesc/internal/XMLScanner.cpp:549:9
14 0xbdadcff in xercesc_4_0::SAX2XMLReaderImpl::parseFirst(xercesc_4_0::InputSource const&, xercesc_4_0::XMLPScanToken&) gdal/xerces-c/src/xercesc/parsers/SAX2XMLReaderImpl.cpp:500:22
```

XERCESC-2219: XMLReader constructor: fix memory leak when refreshRawBuffer() throws

XERCESC-2218: CurlURLInputStream constructor: avoid memory leak

XERCESC-2217: ICUTranscoder::transcodeFrom(): fix read heap-buffer-overflow

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=37529 on GDAL

The backtrace of the exception that caused the memory leak was:
```
Catchpoint 1 (exception thrown), 0x00007ffff5547672 in __cxa_throw () from /lib/x86_64-linux-gnu/libstdc++.so.6
(gdb) bt
0  0x00007ffff5547672 in __cxa_throw () from /lib/x86_64-linux-gnu/libstdc++.so.6
1  0x00007ffff24447c4 in xercesc_4_0::PosixFileMgr::fileRead (this=<optimized out>, f=<optimized out>, byteCount=<optimized out>, buffer=<optimized out>, manager=0x5555556df730)
   at xercesc/util/FileManagers/PosixFileMgr.cpp:160
2  0x00007ffff24e6ec2 in xercesc_4_0::XMLReader::refreshRawBuffer (this=0x5555557e49f8) at xercesc/internal/XMLReader.cpp:1891
3  0x00007ffff24e70d4 in xercesc_4_0::XMLReader::XMLReader (this=0x5555557e49f8, pubId=<optimized out>, sysId=0x555555750920 u"/", streamToAdopt=0x55555574e838, from=<optimized out>,
   type=xercesc_4_0::XMLReader::Type_General, source=xercesc_4_0::XMLReader::Source_External, throwAtEnd=false, calculateSrcOfs=false, lowWaterMark=100, version=xercesc_4_0::XMLReader::XMLV1_0,
   manager=0x5555556df730) at xercesc/internal/XMLReader.cpp:130
4  0x00007ffff24ced75 in xercesc_4_0::ReaderMgr::createReader (this=this@entry=0x5555557896d8, src=..., refFrom=refFrom@entry=xercesc_4_0::XMLReader::RefFrom_NonLiteral,
   type=type@entry=xercesc_4_0::XMLReader::Type_General, source=source@entry=xercesc_4_0::XMLReader::Source_External, calcSrcOfs=false, lowWaterMark=100) at ./xercesc/sax/InputSource.hpp:314
5  0x00007ffff24cb0af in xercesc_4_0::IGXMLScanner::scanReset (this=0x555555789608, src=...) at xercesc/internal/IGXMLScanner2.cpp:1286
6  0x00007ffff24c36e9 in xercesc_4_0::IGXMLScanner::scanDocument (this=0x555555789608, src=...) at xercesc/internal/IGXMLScanner.cpp:198
7  0x00007ffff250abaf in xercesc_4_0::AbstractDOMParser::parse (this=0x7fffffffc2d0, source=...) at xercesc/parsers/AbstractDOMParser.cpp:545
8  0x00007ffff24cbdbe in xercesc_4_0::IGXMLScanner::resolveSchemaGrammar (this=0x555555792f78, loc=0x5555557dd694 u"/", uri=0x555555737180 u"`", ignoreLoadSchema=<optimized out>)
   at xercesc/internal/IGXMLScanner2.cpp:1895
  0x00007ffff24cce7c in xercesc_4_0::IGXMLScanner::parseSchemaLocation (this=0x555555792f78, schemaLocationStr=<optimized out>, ignoreLoadSchema=false) at ./xercesc/framework/XMLBuffer.hpp:171
10 0x00007ffff24cd182 in xercesc_4_0::IGXMLScanner::scanRawAttrListforNameSpaces (this=this@entry=0x555555792f78, attCount=attCount@entry=9) at xercesc/internal/IGXMLScanner2.cpp:1649
11 0x00007ffff24c22cb in xercesc_4_0::IGXMLScanner::scanStartTagNS (this=0x555555792f78, gotData=@0x7fffffffc91f: true) at xercesc/internal/IGXMLScanner.cpp:2213
12 0x00007ffff24c3522 in xercesc_4_0::IGXMLScanner::scanContent (this=0x555555792f78) at xercesc/internal/IGXMLScanner.cpp:890
13 0x00007ffff24c3760 in xercesc_4_0::IGXMLScanner::scanDocument (this=0x555555792f78, src=...) at xercesc/internal/IGXMLScanner.cpp:217
14 0x00007ffff25158e3 in xercesc_4_0::SAX2XMLReaderImpl::parse (this=0x555555731828, source=...) at xercesc/parsers/SAX2XMLReaderImpl.cpp:409
```

ci: Travis uses XCode 12.5

CurlURLInputStream constructor calls the readMore() method, which can
throw exceptions. In that situation, the destructor is not called, which
results in resource/memory leaks. To fix that, catch the exceptions,
manually do the cleanup and rethrow the exceptions.

Found by ossfuzz (locally)

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35373

When charsDecoded == 0, the line ``for (index = 0; index < charsDecoded
- 1; index++)`` will cause to read out of bounds of fSrcOffsets, due to
unsigned integer underflow rules.

Version 4.0.0