Fixed: Missing include directive
The 'use' prevented the build.

There is probably a reason for this line though.
Merge pull request #1424 from 4ZM/master

Changes to make slic3r build on Arch
Removed debugging line
Don't grow horizontal shells having acute angles. #1387
Return Surface objects by reference from SurfaceCollection objects and fix a bug in XS code causing some shell options to be ignored
Fixed wipe (includes regression test). #1421
Optimization
Some minor fixes needed after the xsdata merge. #1421
Fix Only infill where needed putting insufficient material. #1412
Optimization: Remove useless calls to union()
Minor tidying
Some initial work for porting slice()
More porting work
More porting work
Almost finished porting slice()
Fix a bad access after recent change about ->p returning objects by reference
Use the XS slicing code
Move confess_at() to utils.cpp
Untested implementation of split_mesh()