Redirect pointerSize query to the TargetMachine in ASMPrinter

Summary:
Because llvm-dsymutil is using ASMPrinter without any MachineFunction
of Module available.

This change is part of a series of commits dedicated to have a single
DataLayout during compilation by using always the one owned by the
module.

Reviewers: echristo

Subscribers: yaron.keren, rafael, llvm-commits

Differential Revision: http://reviews.llvm.org/D11078

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 242384