Testing for _XCR_XFEATURE_ENABLED_MASK instead of a specific MSVC version because some MSVC 2010 SP1 installations do not have the _xgetbv intrinsic.  Patch thanks to Serge Pavlov!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180125 91177308-0d34-0410-b5e6-96231b3b80d8