Convert the existing regression test scripts for the various optional

PLs to use the standard pg_regress infrastructure.  No changes in the
tests themselves.  Andrew Dunstan

src/pl/plpython/expected/plpython_drop.out

@@ -0,0 +1,5 @@
+--
+-- For paranoia's sake, don't leave an untrusted language sitting around
+--
+SET client_min_messages = WARNING;
+DROP PROCEDURAL LANGUAGE plpythonu CASCADE;