Better handle GL errors in EtcTexture::bind().
Better handle GL errors in EtcTexture::bind().

The scenegraph as a whole does not typically do GL error checking. That
means GL errors occurring elsewhere could cause the etcprovider to unload
textures that loaded correctly.

Change-Id: Ic8e0caa62dab50b391e226cf0a493bc7e357dc46
Reviewed-by: Gunnar Sletta <d0b71651f3efaa9fda200bbcc395b7b82a871fdd@digia.com>

corngood/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,mgrunditz/qtdeclarative-2d,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,corngood/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,matthewvogt/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,corngood/qtdeclarative,corngood/qtdeclarative