Optimize a very hot function by always performing unchecked appends.
When benchmarking 3DFileViewer on my machine, this takes the time spent
in `gl_vertex` down from ~8% to ~2%.
Many of these functions will treat the 'pointer' parameter as an offset
into a buffer if one is currently bound.
This makes it possible to run ClassiCube with OpenGL 1.5 support!
According to the OpenGL 2.0 spec ยง 2.8, the data for each attribute type
pointer is normalized according to the type. The only exception to this
is `glVertexAttribPointer` which accepts a `normalized` parameter, but
we have not yet implemented that API.
According to the spec, enabling the client-side vertex array should
behave as if `glVertex` is executed after all other states such as the
normal, color, etc. have changed. We were not changing these states if
the client-side vertex array was disabled which probably does not affect
a lot of applications, but this seems like the correct thing to do. :^)
According to the spec, pointers to client data need to be dereferenced
immediately when adding calls such as `glDrawElements` or
`glArrayElement` to a display list. We were trying to support display
lists for these calls but since they only invoke _other_ calls that also
support display lists, we can simply defer the display list
functionality to them.
This fixes the rendering of the ClassiCube port by cflip.
When using vertex attribute pointers, we default the Q coordinate for
textures to 0 causing issues if the 4th coordinate is not passed in the
vertex data.
Clean up these defaults and make sure that Q is always set to `1.f`.
