Debugger: Make tooltips pinnable.

Replace old debugger tooltip by a new ToolTipManager which
has a list of AbstractDebuggerToolTipWidget with the functionality
to 'acquire' an engine (display its data) and 'release' it
(store engine data and display them as 'previous') and serialization
to XML session data.
DebuggerTreeViewToolTipWidget implements AbstractDebuggerToolTipWidget
for tree model acting as  a filter on watch models.

Rubber-stamped-by: hjk

src/plugins/debugger/debuggerengine.h

@@ -81,6 +81,7 @@ class ThreadsHandler;
 class WatchHandler;
 class BreakpointParameters;
 class QmlCppEngine;
+class DebuggerToolTipContext;
 
 struct WatchUpdateFlags
 {
@@ -137,7 +138,7 @@ public:
     DebuggerStartParameters &startParameters();
 
     virtual void setToolTipExpression(const QPoint & mousePos,
-        TextEditor::ITextEditor *editor, int cursorPos);
+        TextEditor::ITextEditor *editor, const Internal::DebuggerToolTipContext &);
 
     virtual void updateWatchData(const Internal::WatchData &data,
         const Internal::WatchUpdateFlags & flags = Internal::WatchUpdateFlags());
@@ -183,7 +184,6 @@ public:
 
     virtual void assignValueInDebugger(const Internal::WatchData *data,
         const QString &expr, const QVariant &value);
-    virtual void removeTooltip();
     virtual void selectThread(int index);
 
     virtual void handleRemoteSetupDone(int gdbServerPort, int qmlPort);
@@ -204,6 +204,7 @@ public:
     virtual QAbstractItemModel *localsModel() const;
     virtual QAbstractItemModel *watchersModel() const;
     virtual QAbstractItemModel *returnModel() const;
+    virtual QAbstractItemModel *toolTipsModel() const;
     virtual QAbstractItemModel *sourceFilesModel() const;
 
     void progressPing();
@@ -253,6 +254,8 @@ public:
 
 signals:
     void stateChanged(const Debugger::DebuggerState &state);
+    // A new stack frame is on display including locals.
+    void stackFrameCompleted();
     void updateViewsRequested();
     /*
      * For "external" clients of a debugger run control that needs to do