Some missing ray functions

[recp]

Some missing ray functions:

• glm_ray_sphere(origin, dir, s, &t1, &t2)) -> bool ray sphere intersection
• glm_ray_at(orig, dir, t, &point) point by parameter
• glm_vec3_faceforward(N, I, Nref, dest)
• glm_vec[2|3|4]_reflect(I, N, &dest) reflect
• glm_vec[2|3|4]_refract(I, N, eta, &dest) refract
• tests
• docs

glm_ray_sphere():

• t1 > 0, t2 > 0: ray intersects the sphere at t1 and t2 both ahead of the origin
• t1 < 0, t2 > 0: ray starts inside the sphere, exits at t2
• t1 < 0, t2 < 0: no intersection ahead of the ray
• the caller can check if the intersection points (t1 and t2) fall within a specific range (for example, tmin < t1, t2 < tmax) to determine if the intersections are within a desired segment of the ray

PS: Since there are multiple FPUs on modern CPUs, I see no benefit to use SIMD for reflect() and refract() for now but it is in TODOs for future, not tested but may bring extra overhead, maybe!.