Fixed bad copy and paste causing multiple extruders to throw an error
Free @_ before spawning a new thread (known old Perl bug) as an attempt to fix the unref scalars error
Restore skirt preview and extrude clearance after recent usage of int_offset()
Require the newest Math::Clipper and Boost::Geometry::Utils to avoid the huge memory leaks present in previous versions
Apparent fix for "Attempt to free unreferenced scalar"
Rename do_slice() to quick_slice()
Merge branch 'master' into new-support2