New non-interactive backend: produces .emf files

I just submitted a patch to add a new non-interactive backend that
produces enhanced metafiles, an OpenOffice and Microsoft Windows
scalable graphics format that can also be embedded in .rtf files.

http://sourceforge.net/tracker/index.php?func=detail&aid=1361839&group_id=80706&atid=560722

The backend is based on my pyemf package that I finally released with
its first public beta:

http://pyemf.sourceforge.net

The API should be stable -- I'm only planning on adding to it and not
changing any existing method signatures in the version 2.0.* series.

Oh, and I didn't say so in the patch itself, but I'm happy to donate
the patch to matplotlib under the default matplotlib license.

Rob