mausezahn: change configuration file name to mausezahn.conf

Commit 134a7beb7ab ("mausezahn: re-work configuration file") changed
mausezahn to look for the configuration file in /etc/netsniff-ng. The
filename was intended to be mausezahn.conf not mausezahn.cfg to fit with
the other *.conf file extensions in /etc/netsniff-ng, so change it now.

Signed-off-by: Jon Schipp <jonschipp@gmail.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch> [commit msg edited]
mausezahn: cli.h: increase buffer size

Tobias pointed out and fixed in commit 9ef1dd15551f ("mausezahn:
Increase buffer size for listen address string") that the buffer isn't
log enough to hold the null terminator character. The declaration of the
buffer in cli.h was missed though.

Signed-off-by: Jon Schipp <jonschipp@gmail.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch> [commit msg edited]
man: mausezahn: document configuration file options

Signed-off-by: Jon Schipp <jonschipp@gmail.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>