Ben Gamari authored Mar 23, 2016 and Ben Gamari committed Mar 24, 2016

This adds timings and allocation figures to the compiler's output when
run with `-v2` in an effort to ease performance analysis.

Todo:
  * Documentation
  * Where else should we add these?
  * Perhaps we should remove some of the now-arguably-redundant
    `showPass` occurrences where they are
  * Must we force more?
  * Perhaps we should place this behind a `-ftimings` instead of `-v2`

Test Plan: `ghc -v2 Test.hs`, look at the output

Reviewers: hvr, goldfire, simonmar, austin

Reviewed By: simonmar

Subscribers: angerman, michalt, niteria, ezyang, thomie

Differential Revision: https://phabricator.haskell.org/D1959