Add the "-x" flag to llvm-nm for Mach-O files that prints the fields of a symbol...

Add the "-x" flag to llvm-nm for Mach-O files that prints the fields of a symbol in hex.
(generally use for debugging the tools).  This is same functionality as darwin’s
nm(1) "-x" flag.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213176 91177308-0d34-0410-b5e6-96231b3b80d8