suitable clang stdenv
wip libc++
livcxx build
X11 build purity
build ghc with older binary where possible
mark nixUnstable as broken on darwin
stick darwin-specifics in a conditional
libunwindNative for darwin only
missing an argument
libcxxabi needs coreutils for `cp -d`
fix boost build with clang
fix some packages on darwin
get rid of nasty CC stuff
build nix head successfully
fix even more clang builds
stop copying everything into the store
Merge branch 'darwin-stdenv' of github.com:joelteon/nixpkgs into staging

Conflicts:
	pkgs/development/interpreters/ruby/ruby-19.nix
	pkgs/development/libraries/libc++/default.nix
	pkgs/development/libraries/libc++abi/default.nix
	pkgs/tools/text/sgml/opensp/default.nix
libc++abi: Drop unused Python dependency
llvm: Don't depend on Python on Darwin

There already is a Python in /usr/bin, so we don't need to build
another one.
gcc-wrapper: Remove NIX_GCC_NEEDS_GREP

This is not needed on any currently supported platform.