Teach the symbolizer lib symbolize objects directly.

Currently, the symbolizer lib can only symbolize a file on disk.
This patch teaches the symbolizer lib to symbolize objects.
llvm-objdump needs this to support archive disassembly with source info.

https://bugs.llvm.org/show_bug.cgi?id=41871

Reviewed by: jhenderson, grimar, MaskRay

Differential Revision: https://reviews.llvm.org/D63521

llvm-svn: 365376