Only advertise postSubBuffer extension if we can actually present less than the whole buffer.

This is not available in D3D11, though it is added in D3D11.1.

TRAC #22506

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

git-svn-id: https://angleproject.googlecode.com/svn/branches/dx11proto@1892 736b8ea6-26fd-11df-bfd4-992fa37f6226
6 files changed