I thought I didn't change stdenv, but I did. This will go soon into the stdenv
branch then.
Reverse-merging r16467 through r16465.
svn path=/nixpkgs/trunk/; revision=16468
default, but it didn't happen in Nixpkgs because the string "perl"
appeared in the prefix, and in that case Perl uses $out/lib.
* Enable thread-safe Perl while we're at it.
svn path=/nixpkgs/branches/stdenv-updates/; revision=15252
