Port librfu from firered

sym_ewram.txt

@@ -5,7 +5,9 @@
 	.include "gflib/sprite.o"
 	.include "gflib/string_util.o"
 	.include "src/link.o"
-	.include "src/link_rfu.o"
+	.include "src/AgbRfu_LinkManager.o"
+	.include "src/link_rfu_3.o"
+	.include "src/link_rfu_2.o"
 	.include "src/union_room.o"
 	.include "src/mystery_gift.o"
 	.include "src/union_room_player_avatar.o"