Move the X11 system tray code from widgets into XCB-plugin.

- Add system tray tracker class to XCB plugin and
  provide functionality via invokable slots
  of the native interface.
- Remove XLib-dependency of widgets/utils.
- Reintroduce tracking of tray window destruction
  and recreation, which was removed in the XLib-code
  when porting it from Qt 4 to Qt 5.

This paves the way for implementing the tray icon
completely in terms of QPlatformSystemTrayIcon at some point
later.

Change-Id: Ia04268b0e2919c05874a3e9548930535332897c7
Reviewed-by: Alberto Mardegan <mardy@users.sourceforge.net>
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>
Fix warning in configure about not using 'macx-xcode' for Qt itself

Change-Id: I08f68813ac99f071b6f59a332c99afd75d3de41c
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Assign icons to actions of QTextEdit context menu

Icons are only set if they are valid.

Change-Id: I7637dec18b3066930455a2f6fd40d87097eb20f7
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Assign icons to actions of QLineEdit context menu

Icons are only set if they are valid.

Change-Id: If2398cdc977a3882e7738ef1bcf5519bd7053449
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Laszlo Papp <lpapp@kde.org>
Doc: Unified the summary for C++ classes and QML types.

The placement of the header, since, inherits,
instantiates, and instantiated-by are now in a table.

For C++ classes:
    Header: #include <class name>
    Since: <version>
    Instantiated by: <QML type>
    Inherits: <parent class>
    Inherited by: <list of classes>

For QML types:
    To import: import <QML module>
    Since: <version>
    Inherited by:<list of QML types>
    Instantiates: <C++ class>
    Inherits: <parent QML type>
    Inherited by: <list of QML types>

This is only a part of the work being done for
QTBUG-32172.

Task-number: QTBUG-32172
Change-Id: Ia9d29e824ef7ab4052ea59c6397b5f8fd24022b9
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>