Add accessible role Desktop.

Another role that is mostly needed to make Qt based desktops accessible.
Would be nice to have for KDE's Plasma in the future.

Change-Id: I1d2ce9d55d677f73cc59f0a3646ee5e588c1d948
Reviewed-by: Jan-Arve Sæther <jan-arve.saether@nokia.com>
(cherry picked from commit edc6fae534835a2c72edffb52255fe522a37928f)

src/gui/accessible/qaccessible.cpp

@@ -308,6 +308,7 @@ QT_BEGIN_NAMESPACE
     \value ColumnHeader     A header for a column of data.
     \value ComboBox         A list of choices that the user can select from.
     \value Cursor           An object that represents the mouse cursor.
+    \value Desktop          The object represents the desktop or workspace.
     \value Dial             An object that represents a dial or knob.
     \value Dialog           A dialog box.
     \value Document         A document window, usually in an MDI environment.
@@ -345,6 +346,7 @@ QT_BEGIN_NAMESPACE
     \value StaticText       Static text, such as labels for other widgets.
     \value StatusBar        A status bar.
     \value Table            A table representing data in a grid of rows and columns.
+    \value Terminal         A terminal or command line interface.
     \value TitleBar         The title bar caption of a window.
     \value ToolBar          A tool bar, which groups widgets that the user accesses frequently.
     \value ToolTip          A tool tip which provides information about other objects.

src/gui/accessible/qaccessible.h

@@ -292,6 +292,7 @@ public:
         // Additional Qt roles where enum value does not map directly to MSAA:
         LayeredPane    = 0x0000003F,
         Terminal       = 0x00000040,
+        Desktop        = 0x00000041,
         UserRole       = 0x0000ffff
     };