Add 14th bit to XK_SWITCH_MOD bitmask

The bits of uint signal in an XKeyEvent which concern the key group (keyboard
layout) are bits 13 and 14, as documented here:
https://www.x.org/releases/X11R7.7/doc/libX11/XKB/xkblib.html#Groups_and_Shift_Levels
In the older version, only bit 13 was marked as part of XK_SWITCH_MOD, this
causes issues for users who have more than two keymaps. the 14th bit is not
in ignoremod, key sequences are not caught by match(), if they switch to a third
or fourth keyboard.

x.c

@@ -48,7 +48,7 @@ typedef struct {
 /* X modifiers */
 #define XK_ANY_MOD    UINT_MAX
 #define XK_NO_MOD     0
-#define XK_SWITCH_MOD (1<<13)
+#define XK_SWITCH_MOD (1<<13|1<<14)
 
 /* function definitions used in config.h */
 static void clipcopy(const Arg *);