xkb: Pad structs CommonDoodad and SALockDeviceBtn

xkb: Pad structs CommonDoodad and SALockDeviceBtn

* CommonDoodad is xkbAnyDoodadWireDesc in XKBproto.h. There it has a
  size of 20 like all Doodads:
    #define sz_xkbAnyDoodadWireDesc 20
  Add the necessary 8 bytes of padding.

* SALockDeviceBtn is an Action. All Actions are handled by the server
  and libX11 with sizeof(xkbActionWireDesc) or
  SIZEOF(xkbActionWireDesc). Which results in a size of 8:
    #define sz_xkbActionWireDesc 8 /* in XKBproto.h */
  Add the necessary 3 bytes of padding.

Signed-off-by: Daniel Martin <consume.noise@gmail.com>
Reviewed-by: Ran Benita <ran234@gmail.com>