pam.conf: require pam_loginuid.so

Bug: http://bugs.debian.org/677442
atd.service: Add Documentation field.
atd.service.in: Set IgnoreSIGPIPE=false

Reference: https://bugs.debian.org/756047
Prepare to release at 3.1.15.
Update autoconf.
Merge branch 'master' into debian
Bumped Standards-Version to 3.9.5.
changelog for 3.1.15-1