To facilitate this, add a new hidden command-line option to disable
the explicit-locals pass. That causes llc to emit invalid code that doesn't
have all locals converted to get_local/set_local, however it simplifies
testwriting in many cases.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296540 91177308-0d34-0410-b5e6-96231b3b80d8