matplotlib Code

Fix invalid title string that broke ps output

Handle changed dpi in quiver; remove extra draw in print_figure.
There is still a dpi-related problem with mathtext in the QuiverKey label.

removed backend_agg2

added a dpi callback to the quiver key

fixed dpi figure title positioning problem

Enforce python 2.4 or later; some other version-related cleanup

added numpy version check at build time

Enforce numpy >= 1.1 and python >= 2.3 when importing matplotlib.
Numpy svn passes the test now.

Trying to fix build for Eric (by including png.h first)

Remove a bunch of compiler warnings.