Added ToolTip support for CDB.

Make debugger tooltip API more general, have the engines check the
correct file type, figure out the expression and context from the text
editor.

Put common functionality in watchutils.cpp. In the CDB engine, check
whether a tooltip expression is a known variable within the stack frame
context. If so, retrieve via symbol group or dumpers. Cache by function
and expression.
Reviewed-by: hjk <qtc-committer@nokia.com>

src/plugins/debugger/cdb/cdbdebugengine.h

@@ -60,7 +60,7 @@ public:
                                    QString *errorMessage);
 
     virtual void shutdown();
-    virtual void setToolTipExpression(const QPoint &pos, const QString &exp);
+    virtual void setToolTipExpression(const QPoint &mousePos, TextEditor::ITextEditor *editor, int cursorPos);
     virtual bool startDebugger();
     virtual void exitDebugger();
     virtual void detachDebugger();
@@ -118,6 +118,7 @@ private:
     bool evaluateExpression(const QString &expression, QString *value, QString *type, QString *errorMessage);
     void evaluateWatcher(WatchData *wd);
     void filterEvaluateWatchers(QList<WatchData> *wd, WatchHandler *wh);
+    QString editorToolTip(const QString &exp, const QString &function);
 
     CdbDebugEnginePrivate *m_d;