Fix build with -fno-common

Index: xutils.h
--- xutils.h.orig
+++ xutils.h
@@ -31,11 +31,7 @@ unsigned long	getBlendedColor(char *, float, int, int,
 /*
  * global variables
  */
-Display	*display;
-Window	Root;
-Window 	win, iconwin;
-int	screen;
-int	DisplayDepth;
+extern Display	*display;
 
 /*
  * typedefs