mesa: Set the gl_array_object::ARBsemantics flag at the right time

mesa: Set the gl_array_object::ARBsemantics flag at the right time

With 0963990 the flag was only set when Bind created the object.  In
all cases where ::ARBsemantics could be true, this path never
happened.  Instead, add a _Used flag to track whether a VAO has ever
been bound.  On the first Bind, set the _Used flag, and set the
ARBsemantics flag to the correct value.

NOTE: This is a candidate for release branches.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=45423