Add support for building with new MacOSURLAccessCF NetAccessor that doesn't

require Carbon but can allow Xerces to live soley within CoreServices layer.

Also cleanup detection of various file system capabilities.


git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@173511 13f79535-47bb-0310-9956-ffa450edef68