Add a comment to regress.c explaining what it contains.

Ian Barwick

src/test/regress/regress.c

@@ -1,5 +1,17 @@
-/*
+/*------------------------------------------------------------------------
+ *
+ * regress.c
+ *   Code for various C-language functions defined as part of the
+ *   regression tests.
+ *
+ * This code is released under the terms of the PostgreSQL License.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
  * src/test/regress/regress.c
+ *
+ *-------------------------------------------------------------------------
  */
 
 #include "postgres.h"