MingGW time functions are broken

C:/projects/xerces-c/src/xercesc/util/XMLDateTime.cpp:583:29: error: use of undeclared identifier 'timezone'
        return mktime(&t) - timezone;

Newer versions of MinGW have added functions which were previously missing, like gmtime_r and localtime_r. It's possible the autodetection logic is incomplete and it's not using the correct ifdefs. For Xalan-C, I added additional feature detection and this solved the problem and will work with old or new MinGW versions.