Added seed_krand, and a fix for a potential OOB access in ST_21_FLOOR_DOOR.
Added seed_krand(int32_t* seed), a function for performing RNG that reads from and writes to a custom seed pointer.
Fix undefined behavior/potential OOB access in ST_21_FLOOR_DOOR. g_AnimateGoal does not take a sector number, it takes an animation index, and caps at 1024, not 4096.