Suppress deprecation warnings for GetVersionEx

Visual Studio 12 (2013) deprecated GetVersionEx:

  warning C4996: 'GetVersionExW': was declared deprecated

in favor of either "versionhelpers.h" or VerifyVersionInfo, neither of
which exist in some of the older compilers we support.  Rather than
try to port conditionally to VerifyVersionInfo, simply suppress the
warning for now.

Source/cmGlobalGenerator.cxx

@@ -11,6 +11,9 @@
 ============================================================================*/
 #if defined(_WIN32) && !defined(__CYGWIN__)
 #include "windows.h" // this must be first to define GetCurrentDirectory
+#if defined(_MSC_VER) && _MSC_VER >= 1800
+# define KWSYS_WINDOWS_DEPRECATED_GetVersionEx
+#endif
 #endif
 
 #include "cmGlobalGenerator.h"
@@ -456,7 +459,14 @@ cmGlobalGenerator::EnableLanguage(std::vector<std::string>const& languages,
     OSVERSIONINFO osvi;
     ZeroMemory(&osvi, sizeof(osvi));
     osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
+#ifdef KWSYS_WINDOWS_DEPRECATED_GetVersionEx
+# pragma warning (push)
+# pragma warning (disable:4996)
+#endif
     GetVersionEx (&osvi);
+#ifdef KWSYS_WINDOWS_DEPRECATED_GetVersionEx
+# pragma warning (pop)
+#endif
     cmOStringStream windowsVersionString;
     windowsVersionString << osvi.dwMajorVersion << "." << osvi.dwMinorVersion;
     windowsVersionString.str();