Add expression to build the eboard chess client
Correct patch the rpath for GHC-built executables on Darwin

@peti This addresses #2488.
Build ppl and gmp correctly for building gcc48 on darwin
Fix regression in fetchhg.
haskell-compressed: added 3.10
haskell-singletons: fix tests for darwin
haskell-process-conduit: temporarily disable tests

The tests have not been ported to use conduit-1.1 yet (there is a pull
request pending on GitHub).
Change stdenv on darwin to not set NIX_ENFORCE_PURITY
Making ocropus-hocr run (matplotlib + gdk backend)

I added the gtk backend to matplotlib; if these added dependencies are
too much, we can make this optional.
ocropus: it was still missing a package: lxml

Now "./run-tests" passes. But it can't be run without DISPLAY, so
I don't run it in the builder.
almir: add psycopg2 dependency
nautilus-sendto: add to gnome 3.10
usermount: New Package.

A simple tool to automatically mount removable drives using UDisks2 and
D-Bus.

https://github.com/tom5760/usermount
Plymouth: update to 0.9.0, fix build, sanitize, enable systemd-integration

NOTE: I can start the daemon and ping it, but I haven't been able to
get it to do more than that.
Merge pull request #2789 from matejc/pgsql_almir

almir: add psycopg2 dependency
unbound: update from 1.4.21 to 1.4.22, service from Upstart to systemd
sane: Make SANE_CONFIG_DIR overrideable
spotify: Update from 0.9.4.183.g644e24e.428 to 0.9.10.17.g4129e1c.78 (only for x86_64)
libvpx on darwin: attempt to fix build

CC @lovek323.
arcanist: 20140521 -> 20140530

Signed-off-by: Austin Seipp <aseipp@pobox.com>