Stdenv updates

I'm testing a mass-rebuild branch on Hydra, containing:
 - gcc: 4.8.3 610370f844
 - pkg-config 0.28 #2769
 - grsecurity saga #1187
 - a few minor fixups after these

I'm running wholly on the branch since yesterday. Darwin hasn't rebuilt yet, and I'm not sure if to wait for the thousands of jobs, processing two at once. Comparison to master ("trunk"): http://hydra.nixos.org/eval/1120602?compare=1117862

There are a few errors that I'm unable to reproduce (probably transient). Also this one is likely transient and causing many failures; please restart it if you can: http://hydra.nixos.org/build/11297176

I plan to merge in a few days, unless you stop me ;-)