systemd: Prevent privilege escalation via polkit

Cherry-picked from upstream.  Also applied a fix for the CPUShares
configuration option while I'm at it.

CVE-2013-4327
Revert "asciidoc: add missing dependencies"

This reverts commit aef81d6eb68506426e2004d195125f89922e6a6a.

It's really not good to have every little package that depends on
asciidoc to pull in 1.5 GiB in dependencies (such as Lilypond).
Revert "dblatex: add missing dependencies"

This reverts commit 0350bd3b4853e2b4e3aa4038129073c195c8bef2.  It
causes a huge increase in the closure size of dblatex, since it now
depends on GUI packages like Inkscape.  Also, statically depending on
teTeX might be annoying for people who use TeXlive.