Fix the build with -fno-common

Index: wmgeneral/wmgeneral.c
--- wmgeneral/wmgeneral.c.orig
+++ wmgeneral/wmgeneral.c
@@ -67,6 +67,7 @@ Window		iconwin, win;
 GC			NormalGC;
 XpmIcon		wmgen;
 Pixmap		pixmask;
+Display		*display;
 
   /*****************/
  /* Mouse Regions */