bsp deallocs
poly_split() now takes return args
Update poly_split() callsites
Merge branch 'split-poly-return-args' into bsp_subdivide_to_arrays
WIP: Driving bsp_build() with the new bsp_subdivide() that works on arrays.

The old function is around, and called _bsp_subdivide(), and is called
in clippolygons, still.

The bsp_build() callsite also copies polygons into the tree after the run.
Array driven bsp_build_array() with bsp_build() proxying to it
Tests updated with new calling convention of bsp_build(node, polylist, copy_bool)
BUTT
Merge pull request #15 from sshirokov/bsp_subdivide_to_arrays

Bsp subdivide to arrays, and bsp_build_array