Only initialize some parser regexps once
Don't inherit from Exporter; import 'import' instead
Move lots of eval "" calls to clean package without globals
Convert various eval-related globals to attributes
Convert some instance using functions to methods
Real OO interface

Singleton retained for supporting classical usages.
Test the two new OO variants of PXS operation
Make xsubpp use the PXS OO interface
Update PXS documentation with the OO interface
Document special typemap variables

For better or for worse, these are likely to stay. Don't cry if they
don't.
Regenerate README
MANIFEST update
version bump, changelog