[client] don't print keys to stdout in --save-rc-stanza --key-gen mode

This is a minor commit to not print keys to stdout when both --save-rc-stanza
and --key-gen are set on the command line.
minor documentation updates
minor configure.ac typo fix for --help output
[test suite] minor update to reduce logging noise in valgrind comparison test
update man page in client/server directories to the latest
added HMAC digests section to libfko info doc
[client] allow -D to be used in --save-rc-stanza mode if -n is not given

This change simplifies the fwknop client usage by allowing the -D argument to
be used as the stanza name if -n is not also specified in --save-rc-stanza
mode.
[server] minor update to rename PCAP_ANY_DIRECTION -> ENABLE_PCAP_ANY_DIRECTION