Fix invalid reads by memcmp.
Fix invalid reads by memcmp.

Str may be smaller than Start->Name here. Use strncmp to avoid scanning past the
end. Found by valgrind.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@165157 91177308-0d34-0410-b5e6-96231b3b80d8

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