Set ICU_CXXFLAGS for all files, not just the ICU transcoder, so that special cased code for ICU such as that in RangeToken.cpp, will not break for lack of these flags.

git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@592193 13f79535-47bb-0310-9956-ffa450edef68