constexpr for explicit constructors of vectors and matrices

[RnMss]

e.g.

namespace glm
{
    template <typename T, precision P>
    struct tvec2 {
        ...
        //from 
        //GLM_FUNC_DECL tvec2(T const & s1, T const & s2);`
        //to 
        GLM_FUNC_DECL GLM_CONSTEXPR tvec2(T const & s1, T const & s2);
        ...
    };
}

[Trass3r]

...and quaternions :)

[Groovounet]

This issue should be fixed in master branch for GLM 0.9.8.

Thanks for reporting,
Christophe