Redesign BufferStorage11 to support simultaneously managing constant buffers and vertex/index buffers.

TRAC #22852

Signed-off-by: Geoff Lang
Signed-off-by: Nicolas Capens
Author: Jamie Madill

git-svn-id: https://angleproject.googlecode.com/svn/branches/es3proto@2287 736b8ea6-26fd-11df-bfd4-992fa37f6226