macosx backend: Move all figures to front with non-interactive show()

Dear macosx backend users,

Could you please have a look at pull request https://github.com/matplotlib/matplotlib/pull/1036. It removes a minor annoyance where only the last figure would appear to the front after issuing a non-interactive show().

It builds upon https://github.com/matplotlib/matplotlib/pull/663, delivered with matplotlib 1.1.1.

Cheers,

-Gellule