* Inotify support

  * Inotify support
    - big thanks for Jon Bernard <jbernard@librato.com> for all his help!
  * debian/dirs: add /etc/update-motd directory
  * debian/install: install /etc/update-motd/iwatch.xml
  * debian/iwatch.xml: iwatch configuration file
  * debian/update-motd.cron.d: use the "d" argument for the 10-minute job
  * update-motd:
    - default FREQ to "d"
    - default vars added for inotify
    - usage statement updated accordingly
    - ensure that the cronjobs are no-ops, if running in inotify mode
    - handle starting/stopping inotify via --enable and --disable
    - move the trap to the top, and make sure the lock is established
    - do not run the /etc/update-motd.*/ scripts, if in inotify mode
  * update-motd.1: documentation updated