No API available to pass the supported deviations to the YANG parser

This is related to the implementation of https://bugs.opendaylight.org/show_bug.cgi?id=6261.

I'm looking through the implementation for this, and I don't find anywhere how we can announce to the parser which deviations are supported.

As far as I see from the YANG RFC (e.g. https://tools.ietf.org/html/rfc6020#section-5.6.4.3), the hello message describes which deviations are actually applicable, and to which modules, and only those should be in effect. So we should be able to pass this in the parser, like the list of supported features.