* clutter/clutter-behaviour-depth.c:
Modify to work like all other behvaiours in not forcing
increasing order in behaviour 'limits'. (#436)
Rename limit min/max props to start/end.
* tests/test-depth.c:
Simplify test-case to work with above change and
without multiple ramps
* clutter/clutter-behaviour-rotate.c:
Handle CW rotation when end > start and similar for CCW just
like ellipse behaviour.
* clutter/clutter-behaviour-depth.c: Clarify that what drives
the movement along the Z axis is the ClutterAlpha object (we
don't have the luxury of a rollover like the opacity does);
so, if you want to go from 0 to -100 you have to use a
decreasing function, just as well if you want to go from 100
to 0. Using a min-depth of 100 and a max-depth of 0 and an
increasing function is undefined behaviour.
* tests/Makefile.am:
* tests/test-depth.c: Add a test case for the depth behaviour.
