Debugger: Make DebuggerEngine internal

Expose less of debugger internals to the device plugins.

Change-Id: Ie78756b033fae3fe02bff92eadf26b7319990605
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>
Reviewed-by: Christian Kandeler <christian.kandeler@theqtcompany.com>
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/debugger/debuggermainwindow.h

@@ -36,16 +36,11 @@
 
 #include <utils/fancymainwindow.h>
 
-namespace Core {
-class Context;
-class IMode;
-}
+namespace Core { class IMode; }
 
 namespace Debugger {
-
-class DebuggerEngine;
-
 namespace Internal {
+
 class DebuggerMainWindowPrivate;
 
 // DebuggerMainWindow dock widget names