Ported LayerRegion::make_slices() to XS
Ported GCodeWriter to XS (faster G-code export!)
Bugfix: a move below z_offset was performed when retract_lift was enabled and lift amount was less than z_offset. Includes regression test. #2349
Ported PlaceholderParser::update_timestamp() to XS
Note that Slic3r version number is now located in libslic3r.h
Merge branch 'master' of https://github.com/born2b/Slic3r