[llvm-readobj] Add -elf-section-groups option

Adds a way to inspect SHT_GROUP sections in ELF objects.
Displays signature, member sections of these sections.

Differential revision: http://reviews.llvm.org/D16555

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@258845 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed