GTK+3 blows up on LP64 archs with strict alignment. This comes
down to an unaligned access error in libXi, specifically in
the XIButtonClass case in copy_classes() in XExtInt.c.
cls_lib-num_buttons = cls_wire-num_buttons;
cls_lib-state.mask_len = cls_wire-num_buttons + 7)/8) + 3)/4)
As far as I can see, there are two inconsistent default values for
the ZAxisMapping option for mouse input devices:
* X server: xserver/tree/hw/xfree86/common/xf86Configure.c
Here the default is set to 4 5 6 7, which is what X -configure will
write into a newly created xorg.conf.
* Mouse
