Use new framework for wrapping cat{open,gets,close}(), eliminating

_cat* in the process.
ok kettenis@

src/lib/libc/string/strerror_r.c

@@ -1,10 +1,7 @@
-/* $OpenBSD: strerror_r.c,v 1.9 2015/08/31 02:53:57 guenther Exp $ */
+/* $OpenBSD: strerror_r.c,v 1.10 2015/09/05 11:25:30 guenther Exp $ */
 /* Public Domain <marc@snafu.org> */
 
 #ifdef NLS
-#define catclose	_catclose
-#define catgets		_catgets
-#define catopen		_catopen
 #include <nl_types.h>
 #endif