pull module blacklist from Ubuntu and use it by default

People often have serious problems due to bogus modules like *fb.
lightdm: Update to 1.8.6
lightdm-gtk-greeter: Update to 1.6.1
libarchive: Add extra source URL (close #1655)

It seems that libarchive's home page has not been available for at least the
past couple of days.
pidgin: minor update 2.10.7 -> .8, including CVE-2013-6484

Also switch no newer libstartup-notification, add license and platforms.
openssh_hpn: mark as broken ATM, cf. #1640
gnome3: re-introduce libsoup dependency (fix many evals)
libsoup: enable introspection (gnome3 stuff needs it)

Also some minor refactoring of the expression.
release-small.nix: Disable FreeBSD
libyaml: Patch to fix CVE-2013-6393 (close #1658)
git-daemon service: fix typo in option (close #1659)
libusb1: minor update x-1.0.17 -> 1.0.18 (joined)

The forks joined (or rather libusbx continues under libusb name).
http://sourceforge.net/p/libusb/mailman/message/31886062/
directfb: update from 1.6.2 to 1.6.3

There is a 1.7.x release out but to minimize chances of breaking
dependees I'm only bumping the minimal needed to be compatible with
ilixi (a gui toolkit for directfb that I'm packaging).
directfb: add meta attributes
ilixi: new package

ilixi is a lightweight C++ GUI toolkit for embedded Linux systems.

http://ilixi.org/
python-dpkt: new package

dpkt is a fast, simple packet creation / parsing module, with
definitions for the basic TCP/IP protocols.
bcache-tools: new package

Bcache is a Linux kernel block layer cache. It allows one or more fast
disk drives such as flash-based solid state drives (SSDs) to act as a
cache for one or more slower hard disk drives.

This package contains the required user-space tools.

User documentation is in Documentation/bcache.txt in the Linux kernel
tree.

http://bcache.evilpiepirate.org/
xpra: fix package name

Remove the "python2.7-" prefix from the package name so that it can be
installed with "nix-env -i xpra".
Update cython
Add cython3 (python 3), move cython (python 2) to subfolder