Rufflewind authored May 28, 2015 and Thomas Miedema committed May 28, 2015

Rewrite config/ghc to use getStdout (which use subprocess.Popen) instead
of os.popen, which is deprecated; this also avoids the use of shell

Also:
* Move getStdout to driver/testutil.py so both config/ghc and
  driver/runtests.py can use it

* Remove support for Python below 2.4, which doesn't have subprocess

Reviewed By: thomie

Differential Revision: https://phabricator.haskell.org/D908