Add eapol_version config parameter so folks with clients that (bogusly)
require the authenticator announce EAPOL version 1 don't have to hack
the code to get a working setup.

Discussed with Jouni; he's committed a similar set of changes to
his devel branch and I sent him these changes so I'm committing
this on the vendor branch in the expectation it will appear in
the next import.

MFC after: 1 week