Creatures turned face down by Ixidron maintain all types

When turning creatures face down with [[Ixidron]], their supertypes, card types, and subtypes all remain.

Start by locating the Ixidron implementation and the code that applies face-down status to creatures. Reproduce the issue shown in the report, then trace how supertypes, card types, and subtypes are retained. Done means creatures turned face down by Ixidron no longer retain those types.

Written by the indexing model from the issue text.