hw/xwin: Fix redundant declaration in winprefs.c

winprefs.c:63:14: error: redundant redeclaration of ‘display’
../../include/opaque.h:52:14: note: previous declaration of ‘display’ was here

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Colin Harrison <colin.harrison@virgin.net>

hw/xwin/winprefs.c

@@ -57,9 +57,6 @@ extern int parse_file(FILE * fp);
 /* Currently in use command ID, incremented each new menu item created */
 static int g_cmdid = STARTMENUID;
 
-/* Defined in DIX */
-extern char *display;
-
 /* Local function to handle comma-ified icon names */
 static HICON LoadImageComma(char *fname, int sx, int sy, int flags);