[Glamor] ARB_buffer_storage support

[Grigori Goronzy]

On 13.03.2014 15:04, gongzg wrote:
>
> ARB_buffer_storage is a GL 4.x feature and may not work if the system
> have an older version OpenGL library. Could you modify it to not break
> the old version OpenGL? Thanks.
>

This shouldn't break with OpenGL implementations that don't have 
buffer_storage. AFAIR, I also did a quick test of the fallback path, and 
it worked fine. Does it break for you?

Grigori