elan: Get rid of geometry shader and do geometry clipping manually.
pvr: Aggressively merge transparent polys in per-triangl and OIT mode, duplicating the last vertex to merge opposite cull mode strips.
gl4: reset OIT pointers in final shader. No need for clear pass.
gl4: alternate between 2 buffers for verts.index/tr poly params.
gl4: use gl_VertexID + poly number for poly index.
gl: new GlBuffer class.
20d25059bf