matplotlib Code

Fix memory leaks in ttconv (that manifest themselves in the PDF and PS backends).

Fix a number of minor issues discovered with "-pedantic"

Remove a bunch of compiler warnings.

Fix docstring

Remove "deprecated conversion from string constant to char*" warnings.

Reverting last change since it breaks on gcc-4.2

Attempting to reduce compiler warnings for gcc-4.2 (which I don't
have, but Darren Dale has reported some new warnings).

Improved exception handling. Remove compiler warning.

Convert _ttconv.cpp to use raw Python/C API, rather than CXX.

Add TTF subsetting to backend_pdf.py.