TrayIcon: set the touch mask on the event box, part of SL #4127
TrayIcon: set the touch mask on the event box, part of SL #4127

We do need to add the mask if we want to receive
the 'touch-event' signal. The Gtk.EventBox does
set the touch event mask by default.

[1] http://developer.gnome.org/gtk3/3.4/GtkWidget.html#GtkWidget-touch-event
[2] http://git.gnome.org/browse/gtk+/tree/gtk/gtkeventbox.c#n411

Signed-off-by: Simon Schampijer <088e16a1019277b15d58faf0541e11910eb756f6@laptop.org>
Acked-by: Manuel Quiñones <6f5069c5b6be23302a13accec56587944be09079@laptop.org>

samdroid-apps/sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,gusDuarte/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,tchx84/debian-pkg-sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,gusDuarte/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,gusDuarte/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,gusDuarte/sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,puneetgkaur/backup_sugar_sugartoolkit,sugarlabs/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3