Bugfix: refresh spell availability after MP-crit

Typically, when using a weapon that consumes MP for automatic critical hits (think Punisher, Ogre Nix, Ragnarok, etc), the spell availability of the wielder does not refresh correctly after their attack resolves and their MP updates. This can cause them to be able to select a spell to cast that they cannot actually afford anymore, which is inconsistent with how the game handles a lack of MP normally. This behaviour is especially noticeable if you have a source of counter-attack, such as a Black Belt, as the attack that depletes your MP could happen while you are browsing for a spell to cast!

This Patch fixes this by performing the same operation that would happen after receiving any other source of MP damage (or healing). It makes you unable to select spells that you cannot afford to cast after an MP-crit attack. It does not, however, refresh the text of the open Magic/Lore menus (neither do other MP-affecting effects), so spells will still appear castable that you cannot cast anymore, even though you cannot select them. Closing and reopening the menu does update the spell text correctly.

I tried to fix that too, but got a little lost in the neighborhood of the routine for building the magic menu – so if anyone has any ideas, feel free to take this patch and run with it.

ASM source and IPS patches available on my github here: https://github.com/SirNewtonFig/FF6-mp-crit-refresh