Removed restriction on optimising when infill is being printed before walls.
Removed restriction on optimising when infill is being printed before walls.

By special casing the situation where there are inner insets that don't surround holes,
it's now possible to guarantee that the insets will be printed ordered from inside to
outside which is a requirement when infill is printed before walls.

ROBO3D/CuraEngine,ROBO3D/CuraEngine,Ultimaker/CuraEngine,alephobjects/CuraEngine,ROBO3D/CuraEngine,Ultimaker/CuraEngine,alephobjects/CuraEngine,alephobjects/CuraEngine