compositor: use floats in computing bounding box
compositor: use floats in computing bounding box

In surface_compute_bbox(), call surface_to_global_float() instead of
weston_surface_to_global(). This avoids the recursion:

weston_surface_update_transform()
  weston_surface_update_transform_enable()
    surface_compute_bbox()
       weston_surface_to_global()
         weston_surface_update_transform()

which might be non-obvious when reading the code.

Computing the min and max coordinates in floats, we can have a tight
rounding margin by using floor() and ceil().

Signed-off-by: Pekka Paalanen <6c0263d81461c956d504307112a4ce25eaacc3d1@gmail.com>

Fantu/compositor-spice,jonnylamb/weston,giucam/weston,Fantu/compositor-spice,Gnurou/weston,xorgy/weston,eyolfson/weston,mchalupa/weston,Gnurou/weston,kwm81/weston,udoprog/weston,xorgy/weston,jonnylamb/weston,Tarnyko/weston-xdg_surface_present,eyolfson/weston,mchalupa/weston,krezovic/weston,krezovic/weston,sir-murray/weston,sir-murray/weston,kwm81/weston,Tarnyko/weston-xdg_surface_present,giucam/weston,udoprog/weston,Fantu/compositor-spice