i965: Enable GL_KHR_robustness

i965: Enable GL_KHR_robustness

GL_KHR_robustness adds the GL_CONTEXT_LOST error and five new entry
points that we already implement.  This patch adds a new dispatch table
that returns GL_CONTEXT_LOST from all entry points and implements the
GL_LOSE_CONTEXT_ON_RESET strategy by setting that table when we learn
that we've lost the context.

With the GL_CONTEXT_LOST reporting in place and dispatch for the new
entry points we can turn on GL_KHR_robustness.

Signed-off-by: Kristian Høgsberg Kristensen <krh@bitplanet.net>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Acked-by: Ilia Mirkin <imirkin@alum.mit.edu>