keep track of how artifacts got created

Since the struct used for elements of artiexist[] has a lot of unused
bits, add some new ones to extend it to indicate how artifacts have
been created.  It had
| .exists (has been created) and
| .found (hero is aware that it has been created)
introduce
| .gift (divine gift),
| .wish (player wish),
| .named (naming elven weapon Sting or Orcrist)
| .viadip (made Excalibur by dipping long sword into fountain)
| .rndm (randomly created), and
| .bones (from bones file--how it got created in earlier game isn't
tracked).  The first four are implemented, fifth and sixth aren't.

Some of the feedback when receiving an artifact or spellbook has been
revised.

When artiexist[] was changed from an array of booleans to an array of
structs a couple of days ago, EDITLEVEL should have been incremented
but I overlooked that at the time.  This commit does so now.

src/fountain.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	fountain.c	$NHDT-Date: 1596498170 2020/08/03 23:42:50 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.69 $ */
+/* NetHack 3.7	fountain.c	$NHDT-Date: 1646870844 2022/03/10 00:07:24 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.78 $ */
 /*      Copyright Scott R. Turner, srt@ucla, 10/27/86 */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -404,6 +404,7 @@ dipfountain(register struct obj *obj)
             pline("As the hand retreats, the fountain disappears!");
             obj = oname(obj, artiname(ART_EXCALIBUR), ONAME_FOUND_ARTI);
             discover_artifact(ART_EXCALIBUR);
+            artifact_viadip(obj, TRUE);
             bless(obj);
             obj->oeroded = obj->oeroded2 = 0;
             obj->oerodeproof = TRUE;