Return proper exit code (3) from psql when ON_ERROR_STOP=on and

--single-transaction are both used and the failure happens in commit,
e.g. failed deferred trigger.  Also properly free BEGIN/COMMIT result
structures from --single-transaction.

Per report from Dominic Bevacqua

src/bin/psql/command.c

@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2000-2010, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/bin/psql/command.c,v 1.216 2010/02/26 02:01:17 momjian Exp $
+ * $PostgreSQL: pgsql/src/bin/psql/command.c,v 1.217 2010/03/08 23:03:00 momjian Exp $
  */
 #include "postgres_fe.h"
 #include "command.h"
@@ -1731,10 +1731,28 @@ process_file(char *filename, bool single_txn)
 	pset.inputfile = filename;
 
 	if (single_txn)
-		res = PSQLexec("BEGIN", false);
+	{
+		if ((res = PSQLexec("BEGIN", false)) == NULL)
+		{
+			if (pset.on_error_stop)
+				return EXIT_USER;
+		}
+		else
+			PQclear(res);
+	}
+
 	result = MainLoop(fd);
+
 	if (single_txn)
-		res = PSQLexec("COMMIT", false);
+	{
+		if ((res = PSQLexec("COMMIT", false)) == NULL)
+		{
+			if (pset.on_error_stop)
+				return EXIT_USER;
+		}
+		else
+			PQclear(res);
+	}
 
 	fclose(fd);
 	pset.inputfile = oldfilename;