Support/MachO: Add a bunch of defines.

Right now we have two headers for the Mach-O format. I'd like to get rid
of one. Since the other object formats are all in Support, I chose to
keep the Mach-O header in Support, and discard the other one.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189314 91177308-0d34-0410-b5e6-96231b3b80d8
Move everything depending on Object/MachOFormat.h over to Support/MachO.h.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189315 91177308-0d34-0410-b5e6-96231b3b80d8