hacky OpenGL code to display a quad.

just an initial working version, next up is actually using the
data passed in.
gfx: use an interface for setup/render/cleanup tasks.

so that we don't have to recreate a bunch of crap every frame.
"working" texture setting etc.

doesn't read data from the sim yet. and it also needs to normalize
the floating point value, but it should do that by computing the
max and passing it to a uniform, which is not yet setup yet.
normalize using a uniform.

need to find the uniform's location in Pre(), for some reason.  GL
thinks the uniform name or the program (ambiguous which) is
invalid if I wait until Render().  Strange.  Anyway, I guess the
uniform location should be constant, so this should be faster...

This also doesn't quite seem to work; the texture coordinate
lookup is wrapping badly, or something else awful is happening.
can't quite tell at the moment.
working mallocvis of data for 'heat' program.

hardcoding allocation size still, though.