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.

Change-Id: I85a6547c7dc25a104d4fe9b4034efdc5cea215ef