llvm-objdump: Output line info next to the disassembly if available.

MachO-only at the moment, sorry.

Usage:
$ llvm-objdump -d -m -g -dsym=a.out.dSYM/Contents/Resources/DWARF/a.out a.out
_main:
100000e90:	55	pushq %rbp	## test.c:11:3
…

llvm-svn: 140224