python - be: Squish some bugs.

Log Message:
-----------
Squish some bugs.

One nasty bug that forgot to increment the EmptyPyPgTupleDesc.(Could have been
causing weird failures.)
One that decref'd an object to zero prior to use. =\
Refactor PyPgHeapTuple and PyPgTupleDesc to use the new pattern: PyPgX_NEW.
[More transitions coming later w.r.t. PyPgX_NEW instead of PyPgX_Initialize]

Modified Files:
--------------
be/include/pypg:
cis.h (r1.11 -> r1.12)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/include/pypg/cis.h.diff?r1=1.11&r2=1.12)
heaptuple.h (r1.9 -> r1.10)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/include/pypg/heaptuple.h.diff?r1=1.9&r2=1.10)
query.h (r1.10 -> r1.11)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/include/pypg/query.h.diff?r1=1.10&r2=1.11)
tupledesc.h (r1.9 -> r1.10)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/include/pypg/tupledesc.h.diff?r1=1.9&r2=1.10)
be/src:
function.c (r1.21 -> r1.22)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/function.c.diff?r1=1.21&r2=1.22)
heaptuple.c (r1.15 -> r1.16)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/heaptuple.c.diff?r1=1.15&r2=1.16)
module.c (r1.27 -> r1.28)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/module.c.diff?r1=1.27&r2=1.28)
query.c (r1.20 -> r1.21)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/query.c.diff?r1=1.20&r2=1.21)
tupledesc.c (r1.14 -> r1.15)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/python/be/src/tupledesc.c.diff?r1=1.14&r2=1.15)