Get rid of dependency on lockfile (procmail)

[dagwieers]

Currently rbme requires lockfile, which is part of the procmail package. On some distributions it pulls a complete mailserver as well. We could settle for using flock instead, which is part of util-linux.

[schlomo]

Good idea!

[gdha]

rbme even fails:

+ lockfile -r2 /var/lock/RBME.rbme.lock
/usr/bin/rbme: line 421: lockfile: command not found

[schlomo]

Yes, good point. I'll have to port the code from ReaR.