Patch *WS so that all requests are handled synchronously.

The patch is rather quick and dirty (although not inefficient).
It will require some more care later, but now I'm concerned with
making things work.
Method to undo make_psycopg_green().
Make a couple of shutil methods nice towards gevent.
Avoid using green psycopg when dealing with large files.

Since psycopg (and actually libpq) doesn't support it.
Fix some PEP8 warnings in PsycoGevent.py.
GeventLibrary: interpret _step() call as cooperative yields.