Lay groundwork for generating a log event when finding an artifact
on the floor or carried by a monster. This part should not produce
any change in behavior.
Move g.artidisco[] and g.artiexist[] out of the instance_globals
struct back to local within artifact.c. They are both initialized
at the start of a game (and only used in that file) so don't need
to be part of any bulk reinitialization if restart-instead-of-exit
ever gets implemented.
Convert artiexist[] from an array of booleans to an array of structs
containing a pair of bitfields. artiexist[].exists is a direct
replacement for the boolean; artiexist[].found is new but not put to
any significant use yet. If will be used to suppress the future
found-an-artifact event for cases where a more specific event (like
crowning or divine gift as #offer reward) is already produced.
Remove g.via_naming altogether and add an extra argument to oname()
calls to replace it.
Add an extra argument to artifact_exists() calls.