Upstart 1.13 released

Written for upstart by James Hunt on 2014-07-11

* Fix for handling upgrade from non-stateful-re-exec instance to a
  stateful-re-exec-capable one (LP:#1303891).
* Disable chroot sessions by default. A new '--chroot-sessions'
  command-line option restores the old default behaviour.
* New tests and improved documentation.
* Fix for Session Init umask change on re-exec (LP: #1302117).
* Allow '--confdir' to look for system jobs in multiple
  locations, which also adds new command-line options
  '--append-confdir' and '--prepend-confdir' for full flexibility
  (LP: #1315060).
* Allow initctl(8) commands 'set-env' and 'unset-env' to operate on
  multiple environment variables (LP: #1324096).
* Support for cgroups via a new 'cgroup' stanza. This makes use of
  cgmanager(8) and is available to both System and Session Inits.
  Support for cgroups can be disabled at built-time if required. See
  init(5) for 'cgroup' stanza syntax and examples.