x509: include otherName DER value in GeneralNameInfo
We want to include the whole DER value when we pretty-print
unrecognised otherNames, so add a field to the GeneralNameInfo
namedtuple and populate it for otherNames.
Part of: https://fedorahosted.org/freeipa/ticket/6022
Reviewed-By: Jan Cholasta <jcholast@redhat.com>