The state tracker will call pipe->get_paramf(PIPE_CAP_BITMAP_TEXCOORD_BIAS)
to get a bias factor for adjusting the texcoords used in bitmap/drawpixels.
This allows us to compensate for small differences in rasterization from
one device to another.
The state tracker calls pipe->get_param() to determine the GL limits and
which OpenGL extensions are supported.
This is an initial implementation that'll probably change...