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/debuggermanager.h

@@ -50,6 +50,10 @@ namespace Core {
 class IOptionsPage;
 } // namespace Core
 
+namespace TextEditor {
+    class ITextEditor;
+}
+
 namespace Debugger {
 namespace Internal {
 
@@ -379,7 +383,7 @@ private:
     void toggleBreakpoint(const QString &fileName, int lineNumber);
     void toggleBreakpointEnabled(const QString &fileName, int lineNumber);
     BreakpointData *findBreakpoint(const QString &fileName, int lineNumber);
-    void setToolTipExpression(const QPoint &pos, const QString &exp0);
+    void setToolTipExpression(const QPoint &mousePos, TextEditor::ITextEditor *editor, int cursorPos);
 
     DebuggerRunControl *m_runControl;