Re-land MachineInstr: Reason locally about some memory objects before going to AA.

Summary:
Reverts r311008 to reinstate r310825 with a fix.

Refine alias checking for pseudo vs value to be conservative.
This fixes the original failure in builtbot unittest SingleSource/UnitTests/2003-07-09-SignedArgs.

Reviewers: hfinkel, nemanjai, efriedma

Reviewed By: efriedma

Subscribers: bjope, mcrosier, nhaehnle, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D36900

llvm-svn: 312126