This has several advantages:
1. no more redundant texcoords when we don't need them
2. no more arbitrary limit on how many textures we can bind
3. (that extends to user shaders as well)
4. no more arbitrary limits on tscale radius
To realize this, the VAO was moved from a hacky stateful approach
(gl_sc_set_vertex_attribs) - which always bothered me since it was
required for compute shaders as well even though they ignored it - to be
a proper parameter of gl_sc_dispatch_draw, and internally plumbed into
gl_sc_generate, which will make a (properly mangled) deep copy into
params.vertex_attribs.
Niklas Haas
67fd5882b8