[yaml2obj/obj2yaml] - Support dumping/parsing ABI version.

These tools were assuming ABI version is 0,
that is not always true.

Patch teaches them to work with that field.

Differential revision: https://reviews.llvm.org/D55884

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349737 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed