In a few cases, we set a motion handler just to be able to set a fixed
cursor. This adds a default cursor helper that can be used in those cases.
In case of the 'transformed' test case, we also avoid a brief flicker
of the pointer cursor, which is set on enter when the move grab is lifted.
This new client, called transformed, renders a cross with the top part
red and the right green, with the same transform as the output the
surface is in.
This is based on simple-egl.