Revamp Pokemon Mansion B2F

This was hell to do. There is still one bug in there, and that's the item pickups don't work for some reason. I don't know how these work honestly so if anyone wants to sort that go ahead.

Anyway, some stuff on the map;
- Currently, a warp from B1F leads there, which is intentionally non-returnable. The player walks through the whole map to get to the warp panel. A walk of humanity's shame, if you will. A warp for where the player is meant to go will be necessary later.
- Lore from Japanese media, particularly the first movie's interpretation of Mewtwo, is included. This is based on context clues on its canonicity from LGPE and other bits.
- A clue on how to get the Old Sea Chart is not-so-subtly included.

The MissingNo. event is unfinished, I intend for Martha to deal with that. The text intentionally lacks a "done" bit to force an unpredictable error; I believe this is inconsequential gameplay-wise and should make for a good opening quote when fighting it.

Oh, and Faraway Island has Mankey, Butterfree, and Primeape as find-able Pokemon now. This should be expanded upon later.

data/maps/hide_show_data.asm

@@ -119,7 +119,7 @@ MapHSPointers:
 	dw NoHS
 	dw NoHS
 	dw FarawayIslandInsideHS
-	dw NoHS
+	dw PokemonMansionB2FHS
 	dw NoHS
 	dw NoHS
 	dw NoHS
@@ -571,8 +571,11 @@ SeafoamIslandsB4FHS:
 	db SEAFOAM_ISLANDS_B4F, $03, SHOW
 VermilionDockHS: ; unsure if necessary
 	db VERMILION_DOCK, $01, SHOW
-	;db $FF, $01, SHOW ; end
+	;db $FF, $01, SHOW 
 FarawayIslandInsideHS:
 	db FARAWAY_ISLAND_INSIDE, $01, HIDE ; if mew is fucking up this is why
+PokemonMansionB2FHS:
+	db POKEMON_MANSION_B2F, $03, SHOW
+	db POKEMON_MANSION_B2F, $04, SHOW ; end
 
 	assert_table_length NUM_HS_OBJECTS + 1