This adds multi-column index support for the Python IDL that is
similar to the feature in the C IDL. Since it adds sortedcontainers
as a dependency and some distros don't yet package it, the library
is copied in-tree and used if sortedcontainers is not installed.
Signed-off-by: Terry Wilson <twilson@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
