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
Fix the build broken by r189315.

(this triggered Clang's -Wsometimes-uninitialized on the default path
through the switch)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189319 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "Fix the build broken by r189315." and "Move everything depending on Object/MachOFormat.h over to Support/MachO.h."

This reverts commits r189319 and r189315. r189315 broke some tests on what I
believe are big-endian platforms.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189321 91177308-0d34-0410-b5e6-96231b3b80d8