[llvm-objdump] - Implement the --adjust-vma option.

GNU objdump's help says: "--adjust-vma: Add OFFSET to all displayed section addresses"
In real life what it does is a bit more complicated
(and IMO not always reasonable. For example, GNU objdump prints not only VMA, but also LMA
for sections. And with --adjust-vma it adjusts LMA, but only when a section has relocations.
llvm-objsump does not seem to support printing LMAs yet, but GNU's logic anyways does not
make sense for me here).

This patch tries to adjust VMA. I tried to implement a reasonable approach.
I am not adjusting sections that are not allocatable. As, for example, adjusting debug sections
VA's and rel[a] sections VA's should not make sense. This behavior seems to be GNU compatible.

Differential revision: https://reviews.llvm.org/D57051

llvm-svn: 352347