[MachineOutliner] Add codegen size remarks to the MachineOutliner

Since the outliner is a module pass, it doesn't get codegen size remarks like
the other codegen passes do. This adds size remarks *to* the outliner.

This is kind of a workaround, so it's peppered with FIXMEs; size remarks
really ought to not ever be handled by the pass itself. However, since the
outliner is the only "MachineModulePass", this works for now. Since the
entire purpose of the MachineOutliner is to produce code size savings, it
really ought to be included in codgen size remarks.

If we ever go ahead and make a MachineModulePass (say, something similar to
MachineFunctionPass), then all of this ought to be moved there.

llvm-svn: 342009