Adding <numeric> for GCC 6.x
Adding <numeric> for GCC 6.x

Otherwise you will get something like:

In file included from /<<PKGBUILDDIR>>/src/FffPolygonGenerator.cpp:7:0:
/<<PKGBUILDDIR>>/src/utils/algorithm.h: In function ‘std::vector<long unsigned int> cura::order(const std::vector<_Tp>&)’:
/<<PKGBUILDDIR>>/src/utils/algorithm.h:30:5: error: ‘iota’ is not a member of ‘std’
     std::iota(order.begin(), order.end(), 0); // fill vector with 1, 2, 3,.. etc
     ^~~

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