This moves the code around from one huge file into hopefully logical
and more manageable modules.  For the most part, the code itself was
not touched, except: PLy_function_handler and PLy_trigger_handler were
renamed to PLy_exec_function and PLy_exec_trigger, because they were
not actually handlers in the PL handler sense, and it makes the naming
more similar to the way PL/pgSQL is organized.  The initialization of
the procedure caches was separated into a new function
init_procedure_caches to keep the hash tables private to
plpy_procedures.c.

Jan Urbański and Peter Eisentraut