matplotlib Code

Fix bug in pdf backend (numpy.inf not numpy.infinity)

Update information about mathtext improvements.

Merging mathtext changes into trunk.

Committing in preparation for merge

Important bugfix (many expressions were silently failing)

Support auto-sized delimiters (e.g. \left(\frac{3}{2}\right)).
Commit mathtext_examples.py

rewrote mathext demo to use pythonic api

Fix for get_xheight/get_underline_thickness. Update examples to use
new math syntax.

Got all backends working again. Fixed LaTeX-style fonts, sub/supers,
kerning, spacing around operators, and many other changes.

Back to feature-parity with old mathtext system (plus fractions and no
character clashes).