use uploadTexData() to create init textures w/out data, and restore pixelstorei state on failure

[bsalomon, 2011-12-09 16:30:23]

Two things:

1) Moving all calls to glTexImage2D() to a single function will make it easier
to incorporate glTexStorage2D in a coming change. This is a replacement function
for glTexImage2D and there are some complications about when we can and can't
use it. With this change we'll only have to make the decision in one place.

2) We currently would return in uploadTexData on a GL error but we should
cleanup some glPixelStorei state before exiting the function.

[TomH, 2011-12-09 18:14:39]

LGTM

[bsalomon, 2011-12-09 18:42:00]

Closed with r2844