refactor 'dir = ' into 'set_dir()'

This should have little/no gameplay effect right now, just paving the
 way for directional lights.
Replaced handle_rotation() on buckly things with this.

Signed-off-by: Mloc-Argent <colmohici@gmail.com>

code/WorkInProgress/Chinsky/overmap/ships/engines/thermal.dm

@@ -89,7 +89,7 @@
 	anchored = 1
 
 	New(var/turf/nloc, var/ndir, var/temp)
-		dir = ndir
+		set_dir(ndir)
 		..(nloc)
 
 		if(nloc)