hw/xfree86: Restore API compatibility for cursor loading functions

Create load_cursor_image_check, load_cursor_argb_check,
LoadCursorImageCheck and LoadCursorARGBCheck that can return failure
and use them in preference to the old unchecked variants.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Michael Thayer <michael.thayer@oracle.com>