matplotlib Code

patches: use None rather than 0 for full wedge

patches: allow partial rings with Wedge

fixed a vlines/hlines doc bug

Added missing include, fixed debian bug #505618

Fix autoscaling problems associated with axhline etc.

[ 2269684 ] mathtext broken in the cairo backend

Add comment about minimum positive values.

Update module docstring to include specgram().

Update specgram() to use the new keyword arguments and clean up docstring.

Factor out common core of psd(), csd(), and specgram() into _spectral_helper() function. This allows all of them to have the same calling signature and capabilities and to have the code in a single location.