Adding addtional header files for code generation.
New code generation for gl backends.
New gloo.gl plus autogenerated code.
Changes to gloo to use the new gloo.gl
Various fixes (all tests pass on my machine now).
Flake8
Add notes on code generation/
gl-backend: Robustness++

We pass a big array to opengl and can detect how many values
were written by examining the content. We initialize the array
with bogus values. This commit basically makes the init values
as bogus as they can get: inf for float and the lowest possible
value for int.
Flake8
getUniform getVertexAttrib getTexParameter should not have iv fv suffix.
Fix glReadPixels
Change pyopengl backend to simply import names; speed++

This means that speed comparisons would actually make sense now.
Fix pyopengl api
Change variable name in desktop backend to avoid clash.

It clashed with 'func' in glDepthFunc.
Several fixes in annotations and small improvements in app and gl.use.
Some tests for gl-backends
Newly generated gl backends.
Flake8