[llvm-readobj/llvm-readelf] - Implement GNU style dumper of the SHT_GNU_verneed section.

It was not implemented yet, we had only LLVM style dumper implemented.
Section description is here: https://refspecs.linuxfoundation.org/LSB_2.0.1/LSB-Core/LSB-Core/symverrqmts.html

Differential revision: https://reviews.llvm.org/D62516

llvm-svn: 362080