Revert "Revert "Remove the darwin gdb option, that version of gdb is now dead...

Revert "Revert "Remove the darwin gdb option, that version of gdb is now dead and the rest of the compatibility should be done on a dwarf-N level.""

This reverts commit r189913.

Talked with Eric on IRC. I am going to XFAIL the failing test since it
is using what Eric described as "the member hack" which was needed on
that old GDB.

Sorry for the noise!

llvm-svn: 189914