Use 17 bits for vertex id but substract first vtx index
Use 13 bits for poly number instead of 12
Panzer Front uses more than 4095 tr polys.
Issue #616
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.
Use w=1 to avoid multiply/divide of xy as in dx9
Disable rendering when video output disabled
Use original w value in pixel struct to avoid precision loss (samsptk)
vk oit: missing memory barrier was producing Tr modvol glitches (JSR)
gl oit: Tr modvol needs full vertex shader
Flyinghead