Add getprogname() and setprogname() to ease slackers^porters' work.

Man page adapted from FreeBSD and NetBSD.
Bump libc minor now (there will be more upcoming changes).
input from tedu@
get it in deraadt@

src/include/stdlib.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: stdlib.h,v 1.51 2012/12/03 20:08:33 millert Exp $	*/
+/*	$OpenBSD: stdlib.h,v 1.52 2013/05/31 20:59:24 ajacoutot Exp $	*/
 /*	$NetBSD: stdlib.h,v 1.25 1995/12/27 21:19:08 jtc Exp $	*/
 
 /*-
@@ -270,6 +270,10 @@ int	 getloadavg(double [], int);
 
 void	 cfree(void *);
 
+const char *
+	getprogname(void);
+void	setprogname(const char *);
+
 #ifndef _GETOPT_DEFINED_
 #define _GETOPT_DEFINED_
 int	 getopt(int, char * const *, const char *);