Move 'convertUTF8Sequence' helper into the C++ section of the header file.
Move 'convertUTF8Sequence' helper into the C++ section of the header file.

It's annotated as "inline", but ConvertUTF.c should still be able to compile
as C89.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@173376 91177308-0d34-0410-b5e6-96231b3b80d8

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