Fix multiple memory leaks in PLy_spi_execute_fetch_result: it would leak

memory if the result had zero rows, and also if there was any sort of error
while converting the result tuples into Python data.  Reported and partially
fixed by Andres Freund.

Back-patch to all supported versions.  Note: I haven't tested the 7.4 fix.
7.4's configure check for python is so obsolete it doesn't work on my
current machines :-(.  The logic change is pretty straightforward though.

src/pl/plpython/plpython.c

 /**********************************************************************
  * plpython.c - python as a procedural language for PostgreSQL
  *
- *	$PostgreSQL: pgsql/src/pl/plpython/plpython.c,v 1.141 2010/03/18 19:43:03 petere Exp $
+ *	$PostgreSQL: pgsql/src/pl/plpython/plpython.c,v 1.142 2010/04/30 19:15:45 tgl Exp $
  *
  *********************************************************************
  */
@@ -3147,9 +3147,6 @@ PLy_spi_execute_fetch_result(SPITupleTable *tuptable, int rows, int status)
 
 					PyList_SetItem(result->rows, i, row);
 				}
-				PLy_typeinfo_dealloc(&args);
-
-				SPI_freetuptable(tuptable);
 			}
 		}
 		PG_CATCH();
@@ -3160,11 +3157,15 @@ PLy_spi_execute_fetch_result(SPITupleTable *tuptable, int rows, int status)
 			if (!PyErr_Occurred())
 				PLy_exception_set(PLy_exc_error,
 					   "unrecognized error in PLy_spi_execute_fetch_result");
-			Py_DECREF(result);
 			PLy_typeinfo_dealloc(&args);
+			SPI_freetuptable(tuptable);
+			Py_DECREF(result);
 			return NULL;
 		}
 		PG_END_TRY();
+
+		PLy_typeinfo_dealloc(&args);
+		SPI_freetuptable(tuptable);
 	}
 
 	return (PyObject *) result;