Fix compile problems for mingw compiler.
Fix compile problems for mingw compiler.

totalretribution/CuraEngine,jacobdai/CuraEngine-1,alex1818/CuraEngine,Ultimaker/CuraEngine,mspark93/CuraEngine,fxtentacle/CuraEngine,uus169/CuraEngine,alex1818/CuraEngine,foosel/CuraEngine,markwal/CuraEngine,alephobjects/CuraEngine,patrick3coffee/CuraTinyG,mspark93/CuraEngine,fxtentacle/CuraEngine,pratikshashroff/pcura,ROBO3D/CuraEngine,uus169/CuraEngine,electrocbd/CuraEngine,patrick3coffee/CuraTinyG,totalretribution/CuraEngine,derekhe/CuraEngine,derekhe/CuraEngine,patrick3coffee/CuraTinyG,mspark93/CuraEngine,alephobjects/CuraEngine,ROBO3D/CuraEngine,alex1818/CuraEngine,jacobdai/CuraEngine-1,uus169/CuraEngine,jacobdai/CuraEngine-1,pratikshashroff/pcura,foosel/CuraEngine,alephobjects/CuraEngine,electrocbd/CuraEngine,fxtentacle/CuraEngine,foosel/CuraEngine,pratikshashroff/pcura,markwal/CuraEngine,Ultimaker/CuraEngine,derekhe/CuraEngine,totalretribution/CuraEngine,markwal/CuraEngine,electrocbd/CuraEngine,ROBO3D/CuraEngine