mesa: In core profile, refuse to draw unless a VAO is bound.

mesa: In core profile, refuse to draw unless a VAO is bound.

Core profile requires a non-default VAO to be bound.  Currently, calls
to glVertexAttribPointer raise INVALID_OPERATION unless a VAO is bound,
and we never actually get any vertex data set.  Trying to draw without
any vertex data can only cause problems.  In i965, it causes a crash.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76400
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Cc: mesa-stable@lists.freedesktop.org