Changed --stats implementation to work without -v in only these two
situations:
1. the client is the receiver of files. Can't do it otherwise yet
because without -v the bytes written from the sender's generator
process will not be counted.
2. both the remote and local protocol versions are >=20. I did not
change the protocol version yet because it is such a minor change
that it isn't worth it, although I did test it with the protocol
version set to 20.
If neither of the situations hold, it prints a message saying to use -v.