Add missing include for cstdint to Visibility.h
Add missing include for cstdint to Visibility.h

Summary: We use uint8_t in this header, so we need to include cstdint.

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D47164

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@332913 91177308-0d34-0410-b5e6-96231b3b80d8

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