Powder snow doesn't melt into water in cauldrons

Steps to Reproduce:

1. Place powder snow in a cauldron;
2. Get on fire and walk into the cauldron.

Observed Results:
The powder snow lowers a level.

Expected Results:
The powder snow lowers a level AND becomes water.

Notes: The current behavior can also be considered inconsistent with the full block's behavior, considering the fact that putting out fire with a full block of powder snow melts the entire block instead of just a level.