Debugger: Use the code model to detect unitialized variables.

This should save debugger round trips and crashes in the debugging
helpers.
Add respective option to debugging helper option page, defaulting to
true.On this occasion, make CDB detect shadowed variables correctly
and display them as "<shadowed n>" as does the Gdb engine by
reversing the direction in which
CdbSymbolGroupContext::populateINameIndexMap works.
Rubber-stamped-by: hjk <qtc-committer@nokia.com>

src/plugins/debugger/stackframe.h

@@ -33,12 +33,17 @@
 #include <QtCore/QString>
 #include <QtCore/QMetaType>
 
+QT_BEGIN_NAMESPACE
+class QDebug;
+QT_END_NAMESPACE
+
 namespace Debugger {
 namespace Internal {
 
 struct StackFrame
 {
     StackFrame();
+    void clear();
     bool isUsable() const;
     QString toToolTip() const;
     QString toString() const;
@@ -52,6 +57,8 @@ struct StackFrame
     QString address;
 };
 
+QDebug operator<<(QDebug d, const  StackFrame &);
+
 } // namespace Internal
 } // namespace Debugger