vrend: Use pixel pack buffers as buffers and unbind after use

Closed Gert Wollny requested to merge gerddie/virglrenderer:fix-buffers into master

On one hand it is simpler on GLES, because it allows direct readback, and on the other hand it fixes failures when EXT_texture_buffer is not available.

Also unbind the buffers after use because otherwise glReadPixel would interpret the pixel pointer argument as offset into the pixel buffer and would fail.

Closes: #45 (closed)

Signed-off-by: Gert Wollny gert.wollny@collabora.com

Merge request reports