Add missing --use-existing --help mention from regression binary.

Jan Urba?ski

src/test/regress/pg_regress.c

@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/test/regress/pg_regress.c,v 1.71 2010/02/26 02:01:39 momjian Exp $
+ * $PostgreSQL: pgsql/src/test/regress/pg_regress.c,v 1.72 2010/06/12 17:21:29 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1870,6 +1870,7 @@ help(void)
 	printf(_("                            (can be used multiple times to concatenate)\n"));
 	printf(_("  --dlpath=DIR              look for dynamic libraries in DIR\n"));
 	printf(_("  --temp-install=DIR        create a temporary installation in DIR\n"));
+	printf(_("  --use-existing            use an existing installation\n"));
 	printf(_("\n"));
 	printf(_("Options for \"temp-install\" mode:\n"));
 	printf(_("  --no-locale               use C locale\n"));