Reapply r269782 "[obj2yaml] [yaml2obj] Support for MachO load command structures""

This adds support for all the MachO *_command structures. The load_command payloads still are not represented, but that will come next.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@269808 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed