popover: Set pointer motion mask on the popover window

This is not necessary for the popover itself, but helps tooltips
code confine the widget lookup within the popover if the pointer
is inside it, otherwise the widget lookup may turn out wrong for
motion events, starting the tooltip widget lookup from the toplevel
window, mistakenly triggering tooltips on the natural window
descendants (ie. the widget below the popover)

https://bugzilla.gnome.org/show_bug.cgi?id=724785
Updated Spanish translation
Updated Spanish translation
Updated Norwegian bokmål translation
Updated Norwegian bokmål translation
broadway: Print a useful error message

.. instead of the generic "failed to open display".
separatortoolitem: Make gcc stop complaining

No, a ButtonEvent and a MotionEvent are not the same thing.
reftests: Remove unused argument from function
GtkIconViewAccessible: Don't access freed item

Don't get index from deleted GtkIconViewItem.
Remove the item before traversing list of items.

https://bugzilla.gnome.org/show_bug.cgi?id=701884
gtkmenu: displace popups by their css margin

Without a margin, the pointer is above the first (or last) menu item,
making it easy to accidentally activate that item.

https://bugzilla.gnome.org/show_bug.cgi?id=591258
Updated Brazilian Portuguese translation
gtkentrycompletion: fix a critical warning

There are early returns in this method before the completion timeout
is set later on, so set the source to 0 to avoid trying to remove it
later again.

https://bugzilla.gnome.org/show_bug.cgi?id=725824
popover: dispose popovers when unmanaging them

This makes popovers get rid of dangling pointers at the time of destroying
the relative-to widget, just in case these are kept alive by a reference.