Removed "len" XML attribute from "pointer" parameter declarations of "glVertexAttribIPointerEXT", "glVertexAttribLPointerEXT" and "glVertexAttribPointerARB" commands. The removal was done because the "pointer" parameter is not mean to act as an array, but simply as a relative integer offset when defining vertex attributes. An equivalent fix was done previously for the related commands: "glVertexAttribIPointer", "glVertexAttribLPointer" and "glVertexAttribPointer". (#598)