dbus_cplusplus: fix build with gcc>=4.7, via Gentoo patch
coin3d: fix build with newer gcc
wesnoth: fix build, minor update, parallel builds

Yes, games are the most important things in nixpkgs...
not that I actually plan to play it anytime soon ;-)
perl: disable tests on Darwin, refactor stdenv.lib usage

There was a mysterious error, which I don't have resources to investigate:

Removing test lib/Net/hostent.t
sed: -i: No such file or directory
mu: fix build by using older texinfo
v8: fix build with newer gcc
perl: re-enable the postPatch hook on Darwin

The problem was that sed(1) variants other than GNU sed require a backup suffix
to the -i option.