[Glamor] ARB_buffer_storage support

[Grigori Goronzy]

On 02.03.2014 15:13, Grigori Goronzy wrote:
> These patches use ARB_buffer_storage for persistent mappings. Based
> on Eric Anholt's and Alex Deucher's previous patches. They apply on
> top of Alex's earlier patch series.
>

BTW, to take best advantage of buffer_storage, the minimum VBO size 
should probably be increased (e.g. 256 KB), otherwise the overhead of 
constant reallocation (even if there is a BO cache) reduces performance.

Grigori