vertexAttribIPointer method
Implementation
void vertexAttribIPointer(int index, int size, int type, int stride, int pointer){
  startCheck('vertexAttribIPointer');
  var _pointer = calloc<Int32>();
  _pointer.value = pointer;
  gl.glVertexAttribIPointer(index, size, type, stride, _pointer.cast<Void>());
  calloc.free(_pointer);
  checkError('vertexAttribIPointer');
}