Expression Lists in Declarator Initializers

Verifies expression lists in declarator initializers work correctly.

Shaders are of the form:
  precision mediump float;
  void main() {
      $(type) a, b;
      $(type) c = (b = $(initializer), a = b);
      gl_FragColor = $(asVec4);
  }

Test ensures c, b and a are initialized correctly.