llvm-objdump: add coff import library symbol listing support

llvm-objdump: add coff import library symbol listing support

This adds behaviour similar to binutils' objdump which can show symbols in an
import library.  Differences from that stem around the fact that we do not
create section symbols nor the all import import descriptor symbol reference.
However, this does mean that the tool can serve as a possible replacement for
the existing tool.

llvm-svn: 279088