macOS: Add auto-release pools for Q*ApplicationPrivate::init()

So that any objects autoreleased during application initialization are
released. Otherwise they will end up in the root level pool and only
be released when the application exits and the application goes out
of scope.

Change-Id: If02d24fd70098f9b4b1b0ea3218e0a15e438b9db
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/corelib/kernel/qcoreapplication.cpp

@@ -758,6 +758,10 @@ QCoreApplication::QCoreApplication(int &argc, char **argv
 
 void QCoreApplicationPrivate::init()
 {
+#if defined(Q_OS_MACOS)
+    QMacAutoReleasePool pool;
+#endif
+
     Q_Q(QCoreApplication);
 
     initLocale();

src/gui/kernel/qguiapplication.cpp

@@ -1319,6 +1319,10 @@ void QGuiApplicationPrivate::eventDispatcherReady()
 
 void QGuiApplicationPrivate::init()
 {
+#if defined(Q_OS_MACOS)
+    QMacAutoReleasePool pool;
+#endif
+
     QCoreApplicationPrivate::init();
 
     QCoreApplicationPrivate::is_app_running = false; // Starting up.

src/widgets/kernel/qapplication.cpp

@@ -564,6 +564,10 @@ QApplication::QApplication(int &argc, char **argv, int _internal)
 */
 void QApplicationPrivate::init()
 {
+#if defined(Q_OS_MACOS)
+    QMacAutoReleasePool pool;
+#endif
+
     QGuiApplicationPrivate::init();
 
     initResources();