_gdk_device_get_axis_use() dates back to pre-sealing, when the
xi2 work began, this remaining can be gone with a public
gdk_device_get_axis_use() function already in place.
Previously we weren't installing the device headers when compiling
without XINPUT support. But we would include them from gdkx.h, so
essentially the build was broken.
With this patch the types will exist but not do anything.
Moving the direct-access redefinitions of various macros
to gdkprivate-x11.h and use that header throughout in x11/.
Also remove a workaround for a long-fixed X server bug.
Use the grab and ungrab vfuncs from the frontend instead of the
_gdk_windowing wrappers, and move some things around accordingly.
Again, only the X11 backend has been updated, other backends
need to be updated to match.
