This makes the results of fillPoly align with those of drawPoly when
both are fed whole-pixel coordinates.
For applications where it makes a noticeable difference the offset can
be added manually before calling fillPoly, which is what the vector
font rendering code now does.
Instead of storing everything in a single array delimited by magic
values, have separate arrays containing
- vertices for each polygon
- # of vertices for each polygon
- polygon indices for each char
- # of polygon indices for each char
This arrangement means that multiple char can use reference the same
polygons. build_vector_font.js takes advantage of this by
normalizing and deduplicated polygons where it can.
Shaves exactly one kilobyte from the final build.
