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.
perl: revert "re-enable the postPatch hook on Darwin"

This reverts commit 1778200519a18ae00751ab3015d0e665373c32f6.
Apparently, the sed -i syntax is different from what I thought, because
now the build fails on Darwin, saying:

  sed: -i.bak: No such file or directory

See http://hydra.nixos.org/build/5829944/nixlog/1/raw for more details.
ctemplate: minor update to fix build with gcc>=4.7
ois: fix build with gcc>=4.7 via a Gentoo patch
krb5: minor security update CVE-2002-2443
sonic_visualizer: fix build on newer gcc via a Gentoo patch
slibGuile: fix build via using older texinfo
xorg.xmodmap: fix build via a Gentoo patch
stumpwm: fix build via using older texinfo
pkgs/build-support/cabal: fix the logic of the 'noHaddock' flag that was broken in 27905ce17e1b1aed55edbff5856082b8c1b51fc7
Merge remote-tracking branch 'origin/master' into stdenv-updates.
pkgs/build-support/cabal: unconditionally set $LANG to "en_US.UTF-8" during Haskell builds

Haskell tools like Haddock require a locale to be configured, so do some
regression test suites.
haskell-modular-arithmetic: re-enable the Haddock phase for this package
Merge branch 'x-updates' into stdenv-updates

Conflicts (simple):
	pkgs/development/libraries/glib/default.nix
	pkgs/development/libraries/mesa/default.nix
llvm (merge amend): fix evaluation

Regular binutils now include gold.
binutils: add support for x86_64 in i686 builds (close #857)

Also some style refactoring around repeating "stdenv.lib.optional*".
The author of the idea is @errge.
haskell-diagrams: revert "re-enable haddock documentation"

This reverts commit f735d9801d39ca273f118c31ee6efdae1c81babf.