adds a line when no copyright for Dogecoin Core Developers exists
but the file has been edited by us, to the last year found in git
log, or extends the year range on an existing line when a file
has been modified since the year previously listed.
Excludes subtrees.
mininode now supports witness transactions/blocks, blocktools
has a helper for adding witness commitments to blocks, and script
has a function to calculate hashes for signature under sigversion
1, used by segwit.
Py3 conversion by Marco Falke
Test to make sure upgraded nodes don't ask for non-wit blocks by
Gregory Sanders.
