Make clang-format work in emacs buffers with unicode characters.
Make clang-format work in emacs buffers with unicode characters.

Emacs functions by default use character positions; convert characters
to offsets when handing parameters to clang-format and convert byte
offsets we get from clang-format back to character positions.
Reworked the code a bit so the 0-based to 1-based offset calculations
are done in the same place where we do the multi-byte to offset mapping.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@226445 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,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang