Resolve by welding overaps between adjacent underline glyphs.
Besides avoiding overlap, this makes underlines work better when the
text follows a curve.
Also remove increased underline width which was originally added in [0].
This may have been done to avoid gaps - which is no longer needed.
Further, underlines typically don't extend beyond the glyphs bounds
so the increased width isn't expected behavior.
[0]: a07394ef2c
bcfeeeecda