Emacs darwin: avoid X unless explictly requested

This keeps the dependencies lighter. Perhaps future work on this
derivation could enable the Cocoa interface by default on Mac.
gnuplot darwin: optional gnuplot_aquaterm variant

This variant uses the more Mac-friendly aqua driver, but it requires
that you separately install the AquaTerm package.

Note that AquaTerm is open source and could perhaps be later included
as a nix derivation. If that happens, it would be nice to remove the
gnuplot_aquaterm top-level attribute and just make it the default.
cogl, clutter: update to 1.16.{0,2}
Merge branch 'master' into x-updates

Conflicts (just different styles, same semantics):
	pkgs/development/libraries/libusb1/default.nix
cinnamon: various fixes

cinnamon-translations: use $out/share instead of $out/usr/share,
add version into name

all-packages.nix: refactor
added cinnamon-session
added cinnamon-session.nix
changed gnome-desktop
changed gnome-desktop
poppler: bugfix update 0.24.3 -> .4
libdrm: bump 2.4.49 -> .50

Mainly, it fixes a critical bug for Radeon Southern Islands GPUs.
libsoup: update from 2.44.1 to 2.44.2

Enable introspection
Renamed from libsoup_2_40 to libsoup_2_44
gnuplot: pass aquaterm request explicitely (see #1197)
add webkitgtk 2.2.3

With minor changes from @vcunat, see #1197.
gtk3: bugfix update 3.10.4 -> .5
merge #1197: gnuplot darwin changes
mesa: add myself as a maintainer

When I authored much of the current expression,
I should better watch it, too.
Merge master into x-updates

Conflicts (simple):
	pkgs/top-level/all-packages.nix
fribid: fix build via using gtk2 instead of gtk3

This was caused by a gtk3 update.
I saw they depend on gtk2 instead in Arch and it fixes the build there.
CC @edwtjo
pa_applet: work around a build problem

Also remove wrong homepage.
CC @iElectric.