When infill is not printed every layer, reduce the amount the outline is shrunk.
When infill is not printed every layer, reduce the amount the outline is shrunk.

Normally, the outline is shrunk by 1/2 the infill line width but when infill isn't printed
every layer, the line width is multiplied accordingly and so the outline would be shrunk
too much.

Ultimaker/CuraEngine,Ultimaker/CuraEngine