OS X: Fix positioning of popup menus in case of native NSWindows

The code transformed the coordinates from the view to the window's
content view, and since that content view is flipped in the pure
Qt world (content view == QNSView), it manually flipped the
coordinates to transform from that to window coordinates.

Instead just directly transform the view coordinates to window
coordinates using standard Cocoa methods, which then works with
any kind of content view and NSWindow configuration.

Task-number: QTBUG-40958
Change-Id: Idddd327fe9cff3309606379d0e04ee8b4bd5eece
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
QToolButton: properly reset the size hint when a menu is set on it

QToolButton::sizeHint() takes into account the presence of a menu.
However, setMenu() doesn't retrigger a size hint recalculation. Hence,
(un)setting a menu on an already sized tool button won't properly
reset the size hint. Since the calculated size hint is cached,
delete the cached value and call updateGeometry to cause a
recalculation.

Task-number: QTBUG-38949
Change-Id: I6e79e5e70e31afdfd129282b3668875eca86f51d
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
OSX: emit aboutToShow signal for top-level dock menu.

Qt sets a QCocoaMenuDelegate on every menu it creates in order to emit
the (OSX specific) aboutToShow signal. However, there are a few cases
where OSX will copy a menu without copying the delegate. One of those
cases is the dock: the result of -[NSApplication applicationDockMenu:]
is used to create a new menu, to which a few more items are copied.
This copy is then send back to the dock.

This patch invokes the delegate's -menuWillOpen: method when
-[NSApplication applicationDockMenu:] is called. Note that sub-menus
won't receive the call-back, because the dock doesn't tell the
application what happens after returning from applicationDockMenu:.

Task-number: QTBUG-39604
Change-Id: I0e06df371a3d77342ae4b7148041214e5c4579d7
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>