Update llvm-objdump’s Mach-O symbolizer code for Objective-C references.

This prints disassembly comments for Objective-C references to CFStrings,
Selectors, Classes and method calls.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220500 91177308-0d34-0410-b5e6-96231b3b80d8