This adds support to draw for the new features of transform feedback.
a) fix count_from_stream_output, using max_index+1 for now but it looks
like it should be valid as its derived from the vertex elements/vbo.
b) fix striding and dst offsets in output buffers - was just wrong before.
c) fix cra
I'm not very familiar with these features, but if this passes piglit tests then
it sounds good to me FWIW.
It's however weird that using draw->pt.max_index + 1 (i.e., maximum fecthed
vertex) for count_from_stream_output works in general. I'd imagine it to be
some sort of runtime determined amou
