Upgrade netcat a lot. Make -e able to take the rest of the command line as

Upgrade netcat a lot.  Make -e able to take the rest of the command line as
what to exec.  Add -f mode and a brief explanation of how to use it to replace
minicom.  Add -l -l mode so you can turn any command into a server.  And group
all of netcat's command line options under two CONFIG entries, so if you
disable both it doesn't use getopt at all.