Merge master into stdenv-updates

Conflicts (simple):
	pkgs/development/compilers/gcc/4.8/default.nix
	pkgs/development/compilers/llvm/default.nix
	pkgs/development/libraries/gmp/5.1.1.nix
	pkgs/development/libraries/gmp/5.1.3.nix
	pkgs/development/libraries/gmp/5.1.x.nix
	pkgs/top-level/all-packages.nix