[llvm-readobj] - Refine the LLVM-style output to be consistent.

Our LLVM-style output was inconsistent.
This patch changes the output in the following way:

SHT_GNU_verdef { -> VersionDefinitions [
SHT_GNU_verneed { -> VersionRequirements [
Version symbols [ -> VersionSymbols [
EH_FRAME Header [ -> EHFrameHeader {

Differential revision: https://reviews.llvm.org/D68636

llvm-svn: 375095