do not redownload sources

Signed-off-by: Mattias Andrée <maandree@operamail.com>
complete adaption of sha3sum

Signed-off-by: Mattias Andrée <maandree@operamail.com>
caseless sum comparison

Signed-off-by: Mattias Andrée <maandree@operamail.com>
implement the sha3sum command

Signed-off-by: Mattias Andrée <maandree@operamail.com>