Isolate irrlicht references and use a singleton (#6041)

* Add Device3D class which will contain IrrlichtDevice interface

move getSupportedVideoDrivers to Device3D

Add Device3D singleton & use it in various places

Rename Device3D to Rendering engine & add helper functions to various device pointers

More singleton work

RenderingEngine owns draw_load_screen

move draw functions to RenderingEngine

Reduce IrrlichtDevice exposure and guienvironment

RenderingEngine: Expose get_timer_time() to remove device from guiEngine

Make irrlichtdevice & scene manager less exposed

* Code style fixes

* Move porting::getVideoDriverName, getVideoDriverFriendlyName, getDisplayDensity, getDisplaySize to RenderingEngine

Fix XORG_USED macro -> RenderingEngine + create_engine_device from RenderingEngine constructor directly

* enum paralax => enum parallax

src/clientmap.h

@@ -59,8 +59,6 @@ public:
 	ClientMap(
 			Client *client,
 			MapDrawControl &control,
-			scene::ISceneNode* parent,
-			scene::ISceneManager* mgr,
 			s32 id
 	);