Allows us to un-export DebuggerRunControlFactory in an attempt to
slim down the publicly visible Debugger plugin interface

Change-Id: I0c2e7351ffa7a9d16586172816635be8ff40172e
Reviewed-by: Christian Kandeler <christian.kandeler@theqtcompany.com>
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>
Reviewed-by: BogDan Vatra <bogdan@kde.org>
Reviewed-by: David Schulz <david.schulz@theqtcompany.com>
Reviewed-by: Daniel Teske <daniel.teske@theqtcompany.com>