v0.21

A few tweaks and fixes based on a falexxx1 test from earlier today.

- Don't decrease drop rate for hard and very hard difficulties.  25% on every difficulty now.
- Lessen the rate at which enemy weapon and magic levels increase for hard difficulty.  This should make it notably less difficult.
- Fix an issue where in one out of every 30-40 ROMs the Mana Beast door would get overwritten and end up taking you back to an old floor.

Link