Remove impossible _MSC_VER check
Remove impossible _MSC_VER check

Summary:
It is immediately preceded by this check:
  #if _MSC_VER < 1900
  #error "MSVC versions prior to Visual Studio 2015 are not supported"
  #endif

Reviewers: EricWF

Subscribers: christof, cfe-commits

Differential Revision: https://reviews.llvm.org/D45829

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@330360 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx