Build failure with Windows and VS2013

snprintf isn't available before VS2015, though a Microsoft-specific variant is available which we could use conditionally. However, even this is not present in earlier Visual Studio releases. Do we strictly need to use snprintf here? If we do, how far back do our Visual Studio portability requirements go?

{{

{ 17:53:44 FAILED: C:\PROGRA~2\MICROS~3.0\VC\bin\amd64\cl.exe /nologo /TP -DHAVE_CONFIG_H=1 -DXERCES_BUILDING_LIBRARY=1 -DXERCES_DLL_NAME=\"xerces-c_3_2.dll\0\" -D_THREAD_SAFE=1 -Dxerces_c_EXPORTS -I. -ID:\build\OME-FILES-CPP-DEV-merge-win-superbuild\2a8f6256\build\xerces-source\src -Isrc -ID:\build\OME-FILES-CPP-DEV-merge-win-superbuild\2a8f6256\build\stage\include /DWIN32 /D_WINDOWS /W3 /GR /EHsc /W3 /MD /O2 /Ob2 /DNDEBUG /showIncludes /Fosrc\CMakeFiles\xerces-c.dir\xercesc\util\XMLDateTime.cpp.obj /Fdsrc\CMakeFiles\xerces-c.dir\ /FS -c D:\build\OME-FILES-CPP-DEV-merge-win-superbuild\2a8f6256\build\xerces-source\src\xercesc\util\XMLDateTime.cpp 17:53:44 D:\build\OME-FILES-CPP-DEV-merge-win-superbuild\2a8f6256\build\xerces-source\src\xercesc\util\XMLDateTime.cpp(471) : warning C4244: 'initializing' : conversion from 'time_t' to 'unsigned long', possible loss of data 17:53:44 D:\build\OME-FILES-CPP-DEV-merge-win-superbuild\2a8f6256\build\xerces-source\src\xercesc\util\XMLDateTime.cpp(473) : warning C4244: 'initializing' : conversion from 'time_t' to 'unsigned long', possible loss of data 17:53:44 D:\build\OME-FILES-CPP-DEV-merge-win-superbuild\2a8f6256\build\xerces-source\src\xercesc\util\XMLDateTime.cpp(475) : warning C4244: 'initializing' : conversion from 'time_t' to 'unsigned long', possible loss of data 17:53:44 D:\build\OME-FILES-CPP-DEV-merge-win-superbuild\2a8f6256\build\xerces-source\src\xercesc\util\XMLDateTime.cpp(477) : warning C4244: 'initializing' : conversion from 'time_t' to 'unsigned long', possible loss of data 17:53:44 D:\build\OME-FILES-CPP-DEV-merge-win-superbuild\2a8f6256\build\xerces-source\src\xercesc\util\XMLDateTime.cpp(480) : error C3861: 'snprintf': identifier not found }}

}