Drop genericobject.{cpp,h} (#9629)

* Drop genericobject.{cpp,h}

This file is not for generic object but for ActiveObject message passing.
Put ownership of the various commands to the right objects and cleanup the related code.

* Protect ServerActiveObject::m_messages_out

* typo fix

src/CMakeLists.txt

@@ -384,7 +384,6 @@ set(common_SRCS
 	environment.cpp
 	face_position_cache.cpp
 	filesys.cpp
-	genericobject.cpp
 	gettext.cpp
 	httpfetch.cpp
 	hud.cpp