Allow batching of GL_LINES and GL_POINTS geometry

This is analogous to GL_TRIANGLES and GL_TRIANGLE_STRIP. There is no
reason why we shouldn't batch it. In the case of GL_LINES this means a
slight behavior change, though: If you provided geometry with an uneven
number of vertices, it would draw lines the way opengl specifies it and
drop the last vertex. Now, with batching, it will draw a line from the
last vertex of an "uneven" node to the first vertex of the next node.
This, however, is exactly like it already works for GL_TRIANGLES if you
specify a number of vertices not divisible by 3. We assume the user
should specify a number of vertices that matches the drawing mode.

Change-Id: I372b9c15a19f065d3aeb3727688cca408ce9608e
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>