WIP on new midlines algorithm: can now draw U+aa7a

Now to test with more points.
WIP: Remove debugging code
WIP: Getting still better

Now all endpoints are being handled right. Next up: handling
tripoints (midpoints on intersection triangles). We want to find
the direction, if any, that moves AWAY from the intersection and
draw that if it hasn't already been drawn.
WIP: Now working for U+aa76 and Latin letter R

Some glyphs (like Latin letter X) still appear to be going into an
infinite loop. More work needed, but this is one step closer.