update use of reducers in subdivision.org
add support for vec2/3 seq args in madd/addm, add vec*-op-seq2 fns, add tests
update ds-make-edge-loop to use transients, update bf-edge-points to use new addm seq support
move sd/other-point-in-tri into triangle ns, extract face-loop-triples fn, update catmull-clark & doo-sabin impls
add gmesh PFlip impl
update gmesh tessellate to return new mesh instead of triangle seq