XF86keysym: Add XF86XK_RotationLockToggle

Add XF86XK_RotationLockToggle keysym, to be used as mapping for evdev's
KEY_ROTATE_LOCK_TOGGLE.

I've a Point of View P1006W-232 Windows tablet which actually has a
rotate-lock toggle-button. The latest kernel correctly generates
KEY_ROTATE_LOCK_TOGGLE events for this. So now I'm hooking up support for
it through all the higher layers.
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Jian-Hong Pan <jian-hong@endlessm.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

include/X11/XF86keysym.h

@@ -205,6 +205,8 @@
 
 #define XF86XK_AudioPreset	0x1008FFB6   /* Select equalizer preset, e.g. theatre-mode */
 
+#define XF86XK_RotationLockToggle 0x1008FFB7 /* Toggle screen rotation lock on/off */
+
 /* Keys for special action keys (hot keys) */
 /* Virtual terminals on some operating systems */
 #define XF86XK_Switch_VT_1	0x1008FE01