Reversing through some walls causes softlock

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In particular, vampire cave entrance w/o windmill started, reverse goa (kelbesque entrance), a few of the mt sabre prison cell entrances, and some waterfall cave and mt hydra top-of-screen entrances.

Possible workarounds:

• detect the collision automatically and break down the wall
  • would require a lot of code to do this
• add an extra bit of data somewhere for entrances that set flags?
• edit the map to avoid the softlock
  • moving the entrance/exit up a couple spots doesn't work, so we may need more drastic changes
• simply remove some of the walls?
• add an extra wall to the opposite side with the same flag
  • may need extra map screens, but no free space for it!

For now most of these aren't actual problems, though folks need to be aware of them. They will become much bigger problems once we start randomizing entrances.

[shicks]

Note that if the correct sword is already possessed then none of these are actually a problem, except for vampire cave. So it's possible we can fix them by just ensuring that those locations are blocked on having the right sword (though sword charge glitch changes things).