(mux_printf): Tell GCC that an argument is a printf-style

	format string if HAVE_ATTRIBUTE_FORMAT_PRINTF is set.

src/server/mux.h

 /*
- * $Id: mux.h,v 0.8 1995/01/01 20:17:23 ceder Exp $
+ * $Id: mux.h,v 0.9 1996/07/28 23:32:48 ceder Exp $
  * Copyright (C) 1991, 1993, 1994, 1995  Lysator Academic Computer Association.
  *
  * This file is part of the LysKOM server.
@@ -23,7 +23,7 @@
  * Please mail bug reports to bug-lyskom@lysator.liu.se. 
  */
 /*
- * $Id: mux.h,v 0.8 1995/01/01 20:17:23 ceder Exp $
+ * $Id: mux.h,v 0.9 1996/07/28 23:32:48 ceder Exp $
  *
 ** mux.h
 */
@@ -122,7 +122,11 @@ mux_write(Connection  	       * cp,
 extern int
 mux_printf(Connection  * cp,
 	   const char  * format,
-	   ...);
+	   ...)
+#  if HAVE_ATTRIBUTE_FORMAT_PRINTF
+    __attribute__ ((format (printf, 2, 3)))
+#  endif
+    ;
 #endif
 
 extern int