compositor: weston_surface_assign_output() to use bounding box
compositor: weston_surface_assign_output() to use bounding box

Use the bounding box to compute an approximation of which output
contains most of the surface.

Move the region32 init outside the loop, and fini it, too.

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

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