fix for -f no-common

Index: cmd/wmii/x11.c
--- cmd/wmii/x11.c.orig
+++ cmd/wmii/x11.c
@@ -11,6 +11,9 @@
 #include <bio.h>
 #include "fns.h"
 
+Display *display;
+Screen scr;
+
 Point ZP = {0, 0};
 Rectangle ZR = {{0, 0}, {0, 0}};