doc/standardisation: add rfc6806.txt
doc/standardisation: add rfc6806.txt

Signed-off-by: Stefan Metzmacher <f1988b9e977fc98ae4b41148d1c7fe6accb829c3@samba.org>

madscientist159/heimdal,madscientist159/heimdal,madscientist159/heimdal,madscientist159/heimdal,madscientist159/heimdal,madscientist159/heimdal,madscientist159/heimdal