Merge: gamnit: fix color buffer clearing issues on some computers

Merge: gamnit: fix color buffer clearing issues on some computers

This PR clear the drawing buffers *after* selecting the target framebuffer, even when the buffer does not change. This should fix the issue @BlackMinou was having (the color buffer not being cleared) when running Tinks! 3D or https://gitlab.com/xymus/jumpngun.

However, this does not fix a similar issue on my desktop computer and I think an issue remained with the depth buffer on @BlackMinou computer.

Pull-Request: #2480