Headers: tweak for MSVC[<1800]
Headers: tweak for MSVC[<1800]

Earlier versions of MSVC did not include inttypes.h.  Ensure that we dont try to
include_next on those releases.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@272741 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang