libxss-dev binary package in Ubuntu Precise amd64

 libXss provides an X Window System client interface to the MIT-SCREEN-SAVER
 extension to the X protocol.
 .
 The Screen Saver extension allows clients behaving as screen savers to
 register themselves with the X server, to better integrate themselves with
 the running session.
 .
 This package contains the development headers for the library found in
 libxss1. Non-developers likely have little use for this package.
 .
 More information about X.Org can be found at:
 <URL:http://www.X.org>
 .
 This module can be found at
 git://anongit.freedesktop.org/git/xorg/lib/libScrnSaver

Source package