TINYGL: glBlendFunc Implementation

This PR expands the functionality of TinyGL by adding support to glBlendFunc.
This function enables the user to implement effects such as alpha blending.
The grim engine was also updated to support the feature (and also to support sprite colorization for partial dimming of sprites)
It is used as 0xf81f a few lines above here, could we use either one, or the other?