(show_motd): Printed motd with pr(), as a printf()-like format string!

This reads and formats junk from the stack when motd contains '%', and
can even crash.  Use prnf() instead.

src/lib/player/player.c

@@ -366,7 +366,7 @@ show_motd(void)
     if (tgm.tel_length >= (long)sizeof(buf))
 	tgm.tel_length = sizeof(buf) - 1;
     buf[tgm.tel_length] = 0;
-    pr(buf);
+    prnf(buf);
     (void)close(upf);
     return RET_OK;
 }