headings in option menus

There was a great deal of inconsistency in
different menus on how headings were displayed.
This allows the user to select what they like best.
I was motivated to do this, because I wasn't satisfied
with the appearance of ATR_INVERSE in the menus
on win32tty, and several of them specified it.

src/artifact.c

@@ -692,7 +692,7 @@ winid tmpwin;		/* supplied by dodiscover() */
 
     for (i = 0; i < NROFARTIFACTS; i++) {
 	if (artidisco[i] == 0) break;	/* empty slot implies end of list */
-	if (i == 0) putstr(tmpwin, ATR_INVERSE, "Artifacts");
+	if (i == 0) putstr(tmpwin, iflags.menu_headings, "Artifacts");
 	m = artidisco[i];
 	otyp = artilist[m].otyp;
 	Sprintf(buf, "  %s [%s %s]", artiname(m),