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/breakhandler.h

@@ -42,12 +42,10 @@
 //////////////////////////////////////////////////////////////////
 
 namespace Debugger {
-
-class DebuggerEngine;
-
 namespace Internal {
 
 class BreakpointMarker;
+class DebuggerEngine;
 
 class BreakHandler : public QAbstractItemModel
 {