Remove wrong comment, and fix root cause.

Thanks for noticing the erroneous "-v", Gao Yan!
Systemd mode.
Systemd: add a condition on the configuration file.
Add include of compatibility header file.

See pacemaker commit 6953aa52e00c4ddf481254a828f6d7c7826a23b9 for details.
Compat: resource monitor and newer libpacemaker.

log_cib_diff() moved into compatibility.h, which is not provided in
the package.
Manual page: some systemd hints.
Version 0.1.6.