netsniff-ng: modify mmap option in usage to be grammatically correct

Incorrect usage of "i.e." leads one to believe that replaying is
possible only.

Signed-off-by: Jon Schipp <jonschipp@gmail.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
ifpps: zsh: Add -o option

Add the -o/--omit-header option to ZSH autocompletion.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>