Add a comment on StringRef::contains(char)
Add a comment on StringRef::contains(char)

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@282350 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 9f072db19bc4f674b85c936c7983212c4034030d)

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm