more luck stone ID (trunk only)

more luck stone ID (trunk only)

     Refine yesterday's change in how attempting to assign an artifact's
name to some object works:  only check object descriptions for undiscovered
object types.  Once you know that a particular gray stone is a flint stone,
you could name it "the Heart of Ahriman" as before the previous change.
Conversely, once you learn luck stones, you could give that name to any
other unknown gray stone.  This restores the ability of a player to name
his elven broadsword such that some unsuspecting other player might find
"a runed broadsword named Stormbringer" in a bones file.