Removing Blender Game Engine from Blender 2.8

Folders removed entirely:
* //extern/recastnavigation
* //intern/decklink
* //intern/moto
* //source/blender/editors/space_logic
* //source/blenderplayer
* //source/gameengine

This includes DNA data and any reference to the BGE code in Blender itself.
We are bumping the subversion.

Pending tasks:
* Tile/clamp code in image editor draw code.
* Viewport drawing code (so much of this will go away because of BI removal
  that we can wait until then to remove this.

source/blender/blenloader/intern/versioning_defaults.c

@@ -210,9 +210,6 @@ void BLO_update_defaults_startup_blend(Main *bmain)
 			pset->brush[PE_BRUSH_CUT].strength = 1.0f;
 		}
 
-		scene->gm.lodflag |= SCE_LOD_USE_HYST;
-		scene->gm.scehysteresis = 10;
-
 		scene->r.ffcodecdata.audio_mixrate = 48000;
 	}