We now dereference the pointer given to us before adding the arguments
to an active list. This also factors out the switching logic from the
API wrappers, which helps us with a future commit where we autogenerate
all API wrapper functions.
Each texture unit now has its own texture transformation matrix stack.
Introduce a new texture unit configuration that is synced when changed.
Because we're no longer passing a silly `Vector` when drawing each
primitive, this results in a slightly improved frames per second :^)
