proposal: allow nested function directly in main as the first definition

[choltreppe]

The idea is that this way you are able to use uniforms/in/out in functions other than main.
So something like:

proc testFrag*(
  circleCenter: Uniform[Vec2],
  circleRadius: float32,
  fragPosition: Vec3,
  finalColor: var Vec4,
) =

  proc distanceCircle(pos: Vec2): float32 =
    return length(circleCenter - pos) - circleRadius

  finalColor = vec4(0.0)
  if distanceCircle(fragPosition.xy) < 0:
    finalColor = vec4(1.0)

becomes:

#version 410
precision highp float;
// from testFrag

uniform vec2 circleCenter;
in float circleRadius;
in vec3 fragPosition;
out vec4 finalColor;

float distanceCircle(
  vec2 pos
) {
  float result;
  result = length(circleCenter - pos) - circleRadius;
  return result;
}

void main() {
  finalColor = vec4(0.0);
  if (distanceCircle(fragPosition.xy) < 0.0) {
    finalColor = vec4(1.0);
  }
}

ps: sorry for the fast new commit and PR rename, so there is also the array-uniforms commit