Cyclic include in norm.hpp/quaternion.hpp

[DctrNoob]

A clang-tidy analysis warned me that there's a cyclic include in norm.hpp/quaternion.hpp which is true. norm.hpp has #include "../gtx/quaternion.hpp" while quaternion.hpp has #include "../gtx/norm.hpp".

I don't quiet understand why norm.hpp needs to include the quaternion header so I suspect the include should be removed there though I don't understand the codebase too well to make the final call and raise a PR.