su: Make the su package a provider of only the su binary

Additionally, provide su with the base system and remove su from the
util-linux package as it is now provided by shadow.
teamviewer: fix brokenness after updates / GC

Teamviewer puts symlinks to nix store paths in ~/.teamviewer. When those
paths become garbage collected, teamviewer crashes upon start because of
those broken symlinks. An easy workaround to this behaviour is simply to
delete all symlinks before we start teamviewer. Teamviewer will fixup
the symlinks, just like it did the first time the user ran it.
Merge branch 'cache.su' of git://github.com/wkennington/nixpkgs

su: Make the su package a provider of only the su binary

Fixes #1877
Merge branch 'teamviewer-fix-upgrades' of git://github.com/bjornfor/nixpkgs

teamviewer: fix brokenness after updates / GC
stage1: Systemd libraries were renamed
systemd: Remove shutdown.target.wants
systemd: Upgrade from 203 -> 211
cpupower: Add package to replace cpufrequtils
cpu-freq: Use cpupower instead of cpufrequtils

Additionally, put the powersave utility in charge of loading the
cpufrequency modules based on the governor specified in the
configuration.
systemd: Add slices target
systemd: Add networkd service
stage 1: Remove scsi_wait_scan as it is not supported after kernel 3.7
systemd: Add module path to modules-load
systemd: Update from v211 to nixos-v212