Debugger: Infrastructure for reworked native mixed debugging

- Remove old experimental native mixed approach.
- Move some common stack parsing to Stackhandler.
- Mark gdbbridge.py debug output explicitly to remove it
  from actual reponse handling

New native mixed needs QtDeclarative changes and
QTC_DEBUGGER_NATIVE_MIXED=1 for now.

Change-Id: I09eed1da51cea878636d36756015b7bfaed34203
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>

src/plugins/debugger/debuggerprotocol.h

@@ -252,9 +252,13 @@ enum DebuggerEncoding
     SpecialNotCallableValue                = 36,
     SpecialNullReferenceValue              = 37,
     SpecialOptimizedOutValue               = 38,
-    SpecialEmptyStructureValue             = 39
+    SpecialEmptyStructureValue             = 39,
+    SpecialUndefinedValue                  = 40,
+    SpecialNullValue                       = 41
 };
 
+DebuggerEncoding debuggerEncoding(const QByteArray &data);
+
 // Decode string data as returned by the dumper helpers.
 QString decodeData(const QByteArray &baIn, DebuggerEncoding encoding);