IR printing improvement for function passes - introducing -print-module-scope

Summary:
When debugging function passes it happens to be rather useful to dump
the whole module before the transformation and then use this dump
to analyze this single transformation by running it separately
on that particular module state.

Introducing
    -print-module-scope
debugging option that forces all the function-level IR dumps
to become whole-module dumps.

This option builds on top of normal dumping controls like
   -print-before/after
   -filter-print-funcs

The plan is to eventually extend this option to cover other local passes
(at least loop passes) but that should go as a separate change.

Reviewers: sanjoy, weimingz, silvas, fedor.sergeev

Reviewed By: weimingz

Subscribers: apilipenko, skatkov, llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D40245

llvm-svn: 319561