New feature: hatching of polygons

Currently implemented for PostScript backend only - the rest ignore the command.
I tried to make it in the same style as the rest of Matplotlib iface:
'x' does bidiagonal hatching
'/' does diagonal,
'-' does horizontal,
and so on.
Repeating the hatching symbol increases the density of hatching.

Attached is the diff for version 0.85.
Is there a chance for this thing to be included into the source?

matplotlib.diff (4.24 KB)