Movement speed enhancement and damage repair

Mod/resource Fixed a bug that prevented buffs and damage movement speed from being applied correctly by magic effects.

If you've ever created or used a spell, potion, enchantment, etc. that enhances or harms movement speed, you may have noticed that it doesn't seem to have any effect at all. This is most noticeable with Frost magic, which is supposed to reduce movement speed in half for a few seconds, but it doesn't. It turns out that this is due to the mechanism by which the magic effect changes the speed of movement.

Movement speed is actually determined by two things. The first is a set of speed forms associated with different creatures and movement types, and the second is a character value called a speed multiplier. When something happens, the game recalculates the speed of movement by taking the current movement's speed and multiplying it by a speed multiplier. This is where the problem occurs.

When magic effects change movement speed, it actually works as a speed multiplier on paper, but in practice the game doesn't recalculate movement speed when magic effects are applied or speed multipliers are changed. What /potion/ holds appears to be broken.

This mod solves this problem by attaching a script to all movement speed effects that changes the target of the effect's inventory weight to the target in an instant, and then reverts the change at the start and end of the effect. Since inventory changes do cause the game to recalculate movement speed, this effectively makes the game handle these effects correctly.