Comment 13 for bug 404996

afaict suzumia is right even if I haven't given it much though or tested...
from the rfc: "and therefore
   decoders MAY chose to reject an encoding if the pad bits have not
   been set to zero. The specification referring to this may mandate a
   specific behaviour.
"
so it's no error unless the adc spec requires it and it doesn't (since we know the length of the data we don't need to) so...