Add GLM_FUNC_QUALIFIER to functors in "type_vec4.inl"

[taketwo]

Functors in "type_vec4.inl" are missing GLM_FUNC_QUALIFIER. When compiled with NVCC, this results in a flood of warnings like this:

/home/sergey/third-party/glm/src/glm/detail/type_vec4.inl(418): warning: calling a __host__ function from a __host__ __device__ function is not allowed
          detected during:
            instantiation of "glm::tvec4<T, P> &glm::tvec4<T, P>::operator*=(U) [with T=float, P=glm::highp, U=float]" 
(701): here
            instantiation of "glm::tvec4<T, P> glm::operator*(const glm::tvec4<T, P> &, T) [with T=float, P=glm::highp]" 
/home/sergey/third-party/glm/src/glm/detail/func_packing.inl(76): here

for every operation involving vec4.

[Groovounet]

Thanks for contributing!