This patch allows the PL/Python module to do (SRF) functions.

The patch was taken from the CVS version.

I have modified the plpython.c file and have added a test sql script for
testing the functionality. It was actually the script that was in the
8.0.3 version but have since been removed.

In order to signal the end of a set, the called python function must
simply return plpy.EndOfSet and the set would be returned.

Gerrit van Dyk