Added a couple Clipper tests. #858
Rename t/stl.t to t/slice.t
Added failing test case for troubleshooting unexpected filled holes. #858
Bugfix: some holes being closed incorrectly. #858
Bugfix: PlanePath fill patterns were not working anymore. #880
Add regression test to trap fatal errors during hilbertcurve infill generation. #880
New unit test for layer heights
Refactoring: initialize all layers at once and avoid duplication of slicing height math. #637
Alter extrusion width automatic calculation to take "native flow" into account
Automatic detection of support material threshold angle
Acceleration control. #185
Remove leftover M501
842, 847 slightly enlarge a clip polygon to counteract integer truncation

Geomery in referenced issues triggered Clipper problems, but also
pointed to a situation where integer truncation (as coordinates pass
into Clipper) might be shrinking a clip polygon in a way that leaves
degenerate or unwanted thin clip results. Growing the clip polygon by 2
is expected to overcome any issues caused by truncation of floats.
Bugfix: crash when reading/writing files to paths containing non-ASCII characters on Windows. #651 #865
offset miter limit to 3 - 801 828 836 851 875 - spikes and pimples

Was set to 10 to address 801. Setting to 3 has the same effect for 801,
and avoids spike artifacts that are likely causing "spike and pimple"
problems in the referenced issues.
extraneous fill against sloped walls with fill every N layers #834

Polygons used for N x depth fill surfaces need to be offset
by flow spacing before they are reused to clip lower fill surfaces.
Otherwise thin fill sections remain on clipped layers against sloping
walls, and the N x depth fill collides with them.
Ignore perimeter_acceleration and infill_acceleration if their values are 25 and 50 to handle legacy configs gracefully.
use infill flow spacing, not perimeter, for combine_infill() clip offsets
Merge branch '834-every-n-fill-frags' #834
per-thread clipper object for parallel support generation #888