Fix GLES 2 after the multiple-texture-rectangle branch merge

Fix GLES 2 after the multiple-texture-rectangle branch merge

The GLES 2 wrapper needs to set up some state before each
draw. Previously this was acheived by wrapping glDrawArrays. Since the
multiple-texture-rectangle branch merge, glDrawElements is used
instead so we also need a wrapper for that.

It was also directly calling glBindTexture. GLES 2 uses a wrapper for
this function so that it can cope with GL_ALPHA format textures. The
format of the current texture needs to be stored as well as the target
and object number for this to work.