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.

constants/map_constants.asm

@@ -135,7 +135,7 @@ DEF FIRST_INDOOR_MAP EQU const_value
 	mapconst LANCES_ROOM,                   13, 13 ; $71
 	mapconst FARAWAY_ISLAND_OUTSIDE,                  18,  15 ; $72	; Unused UNUSED_MAP_72
 	mapconst FARAWAY_ISLAND_INSIDE,                  11,  15 ; $73	; Unused UNUSED_MAP_73
-	mapconst POKEMON_MANSION_B2F,                  8,  8 ; $74	; Unused UNUSED_MAP_74
+	mapconst POKEMON_MANSION_B2F,                  12,  15 ; $74	; Unused UNUSED_MAP_74
 	mapconst UNUSED_MAP_75,                  0,  0 ; $75	; Unused
 	mapconst HALL_OF_FAME,                   4,  5 ; $76
 	mapconst UNDERGROUND_PATH_NORTH_SOUTH,  24,  4 ; $77