Minor aesthetic fix
Add ARM64.xcodeproj

I also added the ARM64 target sources, as well as the
ARM64CommonTableGen and libLLVMARM64CodeGen targets.
Fix warnings
Add LLVMARM64Info
Add LLVMARM64AsmParser
Fix warning
Add LLVMARM64Disassembler
Add LLVMARM64AsmPrinter
Add LLVMARM64Desc