pgsql: Add table_name and table_schema to plpython trigger data, plus

Log Message:
-----------

Add table_name and table_schema to plpython trigger data, plus docs and regression test.

Modified Files:
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pgsql/doc/src/sgml:
plpython.sgml (r1.29 -> r1.30)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpython.sgml.diff?r1=1.29&r2=1.30)
pgsql/src/pl/plpython:
plpython.c (r1.79 -> r1.80)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/plpython.c.diff?r1=1.79&r2=1.80)
pgsql/src/pl/plpython/expected:
plpython_function.out (r1.6 -> r1.7)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/expected/plpython_function.out.diff?r1=1.6&r2=1.7)
pgsql/src/pl/plpython/sql:
plpython_function.sql (r1.6 -> r1.7)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/sql/plpython_function.sql.diff?r1=1.6&r2=1.7)