Turn some Twine locals into const char * variables.
Turn some Twine locals into const char * variables.

No functionality change, just stylistic cleanup. Change made by clang-tidy
and clang-format.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@212544 91177308-0d34-0410-b5e6-96231b3b80d8

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