zero-init signals array

Closes https://github.com/mate-desktop/mate-applets/pull/108
avoid dereferencing NULL pointer

Closes https://github.com/mate-desktop/mate-applets/pull/114
drivemount: Fix "variable might be used uninitialized"

The code used to set a broken screen in an error case.

Based on gnome-applets commit: 33e10c46f76994a94fbccb8da0acb4ca36e6f20a
From: Benjamin Otte <otte@redhat.com>
stickynotes: Fix compile warnings

Based on gnome-applets commit: 18e23a490529131d17c931247481cfa02b1f14b3
From: Benjamin Otte <otte@redhat.com>
stickynotes: we do not use the status anywhere so it has to go.
stickynotes: Small fixes for warnings etc
stickynotes: Remove redundant store of root_window.
batstat: Use cairo for drawing also in Gtk2.
battstat: Suggest parenthesis around assignment used as truth value

Based on gnome-applets commit: 3d51417f06ac5e4177e22ff970d7906e2802ff48
From: Benjamin Otte <otte@redhat.com>
battstat: add missing function declaration

Based on gnome-applets commit: 5d6f1a6d3888bd4d4f4ea6288d99a79c1dd63442
From" Alberts Muktupāvels <alberts.muktupavels@gmail.com>
docs: Fix typo
batstat: sync upower code with gnome-applets.

Largely taken from: gnome-applets commit: 95ff3ab8dfb5f595263dce6857b7d5935042e336
From: Dmitry Shachnev <mitya57@gmail.com>
Gtk3: Silence GtkVbox and GtkHbox deprecation warnings
Gtk3: don't use deprecated gtk_widget_size_request

Taken from gnome-panel commit: c05c6b07ec493d174062a06caf185d324fd6e0c4
From: Alberts Muktupāvels <alberts.muktupavels@gmail.com>
GDK_KEY_* is also in Gtk+2
cpufreq: Add missing #include <config.h> to make translations work
cpufreq: Bring gsettings code in line with gnome-panel

Taken from 6d61304f8ee62eb2776725b8424140a332f651cf
drivemount: do not show shadowed mounts

Based on gnome-applets commit: f7cd488eae7d25c0b2be6a709bc5ebf0420cd165
From: Aleksander Morgado <aleksander@lanedo.com>
Gnome bug: https://bugzilla.gnome.org/show_bug.cgi?id=622709
drivemount: allow unmount without eject

Based on gnome-applets commit: be2f99f0e4dfee124e380cd6d303bae3372c088b
From: Enrico Minack <enrico-minack@gmx.de>
Gnome bug: https://bugzilla.gnome.org/show_bug.cgi?id=604848
geyes: Just use GSourceFunc for both Gtk+ versions