Fix "(very) rotten" shown for corpses in ice boxes

peek_at_iced_corpse_age() was not considering corpses in ice boxes,
leading to this incorrect object name annotation.

Curiously, corpses in a bag then placed in an ice box still rot, since
there's no check to stop timers on container-nested corpses.

This bug also exists in UnNetHack (only seen with DYWYPISI).
NH4: Clean up CMakeLists.txt for data directory

Compared to NetHack4, this includes UnNetHack's new levels; last I
counted, there were over 80 of them.  The game doesn't check if all of
the compiled special levels are present until it wants to make them, so
it's possible that I accidentally left some out of nhdat; there should
be a level name for every "LEVEL:" line in each *.des file.

Clean up cmake file for data directory.
Marcin Kościelnicki <koriakin@0x04.net>
178d9d3fd2e86cd725259363cc4e7b30afb0618e