more issue #1303

Various bits I had in progress before Michael's commit.

Mainly forget engravings when bones are saved instead of leaving them
flagged as seen for the next hero who gets the level.

src/bones.c

@@ -445,6 +445,7 @@ savebones(int how, time_t when, struct obj *corpse)
     iter_mons(remove_mon_from_bones); /* send various unique monsters away, */
     dmonsfree();                      /* then discard dead or gone monsters */
 
+    forget_engravings(); /* next hero won't have read any engravings yet */
     /* mark all named fruits as nonexistent; if/when we come to instances
        of any of them we'll mark those as existing (using goodfruit()) */
     for (f = gf.ffruit; f; f = f->nextf)