Silence all C4592 warnings with MSVC 2015 Update 1. This warning produces...

Silence all C4592 warnings with MSVC 2015 Update 1. This warning produces false positives that Microsoft says will be fixed in Update 2. Until this produces reliable diagnostics, it is safe to disable the diagnostic -- the compiler is not doing anything different than it previously did aside from issuing the diagnostic.

(Note, this silences at least one false positive in LLVM with FeatureBitset uses.)

llvm-svn: 254915