stdenv: Remove the special handling of gcc

Now gcc is just another build input, making it possible in the future
to have a stdenv that doesn't depend on a C compiler. This is very
useful on NixOS, since it would allow trivial builders like
writeTextFile to work without pulling in the C compiler.
stdenv: Reindent
Prevent an unnecessary evaluation of lib
stdenv: Don't use sed to build the setup script
Remove addHook

Just use bash arrays directly. I.e.

  addHook preConfigure myPreConfigure

is now

  preConfigureHooks+=(myPreConfigure)
Allow passing arguments to hooks

This allows envHooks and crossEnvHooks to be handled using the regular
hook mechanism.
fixupPhase: Fix making the outputs writable
Cleanup: Use += to append to envHooks
stdenv: Put moving docs to $out/share in a separate setup hook
Move share/{man,info,doc} to the corresponding output
systemd: Update to 216
systemd: Build manpages
systemd: Drop unnecessary dependency
NixOS containers: Use exit status 133 for reboots
Doh
Enable systemd's mymachines NSS module

It makes every local container registered with machined resolvable.
polkit: Add docbook DTD
Merge remote-tracking branch 'origin/master' into systemd-216
Merge remote-tracking branch 'origin/systemd-216' into staging
merge 'staging' into modular-stdenv

In 2c62a36b77 the messages in pkgs/stdenv/generic/default.nix
were not merged correctly.

Conflicts:
	pkgs/stdenv/generic/default.nix