loginManager.js: Use a normal signal connection for PrepareForSleep.

Update the calendar and power applets to refresh on resume, and
update the ScreenShield to connect to the signal directly.

The UPowerGLib.Client code in the calendar applet has been dead code
since 0.99 (notify-resume signal was removed and the 'resume' property
was never never a thing).

cinnamonEntry.js: Allow addContextMenu() to re-use an existing

PopupMenuManager.

If the St.Entry is inside of a popup menu (and *not* a modal dialog),
that menu's 'captured-event' handler can receive unintended events,
and react to focus loss, closing both the original popup and context
menu.

The original menu's manager can safely deal with multiple popups,
and ensure 'correct' behavior in this situation.

ref:
#13472

Silence some gir-2.0-related warnings.

Silence some gir-2.0-related warnings.