direction over multiple regions. This allows a single bridge to be
drawn over holes, which are too close to each other to allow
for separate bridges.
Fixes Bridging-Angle not optimal
https://github.com/prusa3d/Slic3r/issues/12
Re-allowed adaptive infill line width for solid infills. The adaptive
infill line width works in some circumstances, see Issue #15,
but the original implementation often changed the line width too
aggressively. The current implementation limits the line width change
to 20%.
Fixes Gaps between infill and perimeter leads to errors in laydown on following layer
https://github.com/prusa3d/Slic3r/issues/15
