Added support for querying client attribute state through `glGet*`.
All the `glGet*` calls will first see if the attribute passed in is an attribute recognized by `glEnableClientState`
and if so, will retrieve that from `GL.immediate.enabledClientAttributes`.
Otherwise, it will call into WebGL for the value of the attribute.
Modified test included.
Added symbols for the OES versions of the VertexArrayObject calls.
Merge branch 'support-querying-client-state' into add-all-missing-symbols
Merge branch 'incoming' of https://github.com/kripken/emscripten into add-all-missing-symbols
Merge commit '32a17b0a1b5f5dd1038fdd9b9e79c17b6687a5d3' into incoming

Conflicts:
	src/library_gl.js