This commit bumps the fwknop version to 2.5 and sets the libfko version to 2.0 to
signal incompatibility with older libfko versions. Backwards compatibility is
maintained in SPA packet construction, but function prototypes in libfko-2.0 are
no longer compatible with older versions.
This commit also returns non-zero exit status under 'fwknopd --status' if there
is no existing fwknopd process. This is better than always exiting with a zero
status regardless of whether fwknopd is already running or not, and adds a level
of scriptability to --status usage. This change was suggested by George Herlin.
37b624ac8b