CurveIterator is wrong with curves starting with OFF point

[rbrich]

According to freetype docs, the contour may start with conic off point. This case is not handled by CurveIterator, which assumes that first point is always on curve.

I encountered the problem with FreeSans.ttf, glyph "0". The inner contour has these tags: 00101001. The first point is conic off, so the last point should be used instead as the curve's starting point.

This is my render of the wrong outline:

Another example is the glyph for "8", the tags are 00010010010, ie. both ends of the contour are off-curve.

[rbrich]

Another bug is in ContourIterator.from_raw(). When outline.n_contours is 0, then last_end_idx is set to outline.contours.offset(-1) and the iterator crashes in next() method. This happens for space character, which has no countours.