Debugger[gdb]: Improve reporting of Windows exceptions.

Particularly affecting Windows DLL loading, which was previously
suppressed.

Reviewed-by: hjk
Task-number: QTCREATORBUG-3470

src/plugins/debugger/gdb/gdbengine.h

@@ -561,6 +561,7 @@ private: ////////// View & Data Stuff //////////
     // HACK:
     StackFrame m_targetFrame;
     QByteArray m_currentThread;
+    QString m_lastWinException;
 };
 
 } // namespace Internal