Updates.

* Support use of new org.freedesktop.login1.Manager for sleep/resume signals.
  But fallback to UPower signals (for Ubuntus older than 13.10).
* Add doc for NetworkManager state signal numbers.
* Only apply removal of XMODIFIERS variable when Emacs version <= 24.3.
* Don't assume output of Emacs instance startup should go to ~/.xsession-errors.
* Make major/minor versions available as variables in script.