Add API for frustum-based projection

[Eggbertx]

As it is now, we have orthogonal projection (via Transform#project2D) and frustum projection (via Transform#project3D), but it would be nice to have perspective projection as well. This can be done by using GLM, which also adds other transform and matrix related functions like lookAt (which can use 2D or 3D vertices). It's written in C++, but in my experience, it works reasonably well with plain C.

[fatcerberus]

Wait, there’s a difference? I always thought perspective and frustum were the same.

[Eggbertx]

Actually scratch that, project3D is technically perspective (using FOV, aspect, and near/far values), frustum projection would be using left, right, top, bottom, near, and far planes.