gold dragon and scales

Add two new monsters and two new objects:
 gold dragon
 baby gold dragon
 gold dragon scale mail
 set of gold dragon scales

A couple of variants seem to have added these already, but this came
off my ancient list of monsters to add and was done from scratch.
It's a clone of silver dragon, but instead of having reflection and
breathing cold, a gold dragon emits light and breathes fire; because
of the latter it can be seen with infravision like a red dragon.
Adult gold dragons are lawful as in the AD&D Monster Manual rather
than chaotic as the wiki pages show for the variant versions.

Worn gold dragon scales operate similar to wielded Sunsword:  when
blessed, radius is 3 (same as a lamp), if uncursed, radius is 2, and
if cursed, radius is 1 (but functions as 2 when worn by the hero,
otherwise there would be no tangible effect).  Gold dragon scale mail
gets an extra +1, making blessed gold DSM have a bigger radius than
lamps.  Embedded scales have radius 1 regardless of BUC state; light
for that case comes from the gold dragon monster form the hero is in.
When not worn, gold scales and scale-mail don't emit any light.

The tiles use a mix of yellow (for gold) and red.  The two object
tiles seem reasonable variations of the corresponding silver dragon
ones.  The two monster tiles definitely need work since the silver
ones were mostly cyan and changing that to red did not produce very
good result; subsequent attempt at a mixture was haphazard at best.

src/worn.c

@@ -528,8 +528,9 @@ m_dowear_type(struct monst *mon, long flag, boolean creation,
               boolean racialexception)
 {
     struct obj *old, *best, *obj;
+    long oldmask = 0L;
     int m_delay = 0;
-    int unseen = !canseemon(mon);
+    int sawmon = canseemon(mon), sawloc = cansee(mon->mx, mon->my);
     boolean autocurse;
     char nambuf[BUFSZ];
 
@@ -629,13 +630,15 @@ m_dowear_type(struct monst *mon, long flag, boolean creation,
         m_delay += 2;
     /* when upgrading a piece of armor, account for time spent
        taking off current one */
-    if (old)
+    if (old) {
         m_delay += objects[old->otyp].oc_delay;
 
-    if (old) /* do this first to avoid "(being worn)" */
-        old->owornmask = 0L;
+        oldmask = old->owornmask; /* needed later by artifact_light() */
+        old->owornmask = 0L; /* avoid doname() showing "(being worn)" */
+    }
+
     if (!creation) {
-        if (canseemon(mon)) {
+        if (sawmon) {
             char buf[BUFSZ];
 
             if (old)
@@ -654,20 +657,45 @@ m_dowear_type(struct monst *mon, long flag, boolean creation,
         if (mon->mfrozen)
             mon->mcanmove = 0;
     }
-    if (old)
+    if (old) {
         update_mon_intrinsics(mon, old, FALSE, creation);
+
+        /* owornmask was cleared above but artifact_light() expects it */
+        old->owornmask = oldmask;
+        if (old->lamplit && artifact_light(old))
+            end_burn(old, FALSE);
+        old->owornmask = 0L;
+    }
     mon->misc_worn_check |= flag;
     best->owornmask |= flag;
     if (autocurse)
         curse(best);
+    if (artifact_light(best) && !best->lamplit) {
+        begin_burn(best, FALSE);
+        vision_recalc(1);
+        if (!creation && best->lamplit && cansee(mon->mx, mon->my)) {
+            const char *adesc = arti_light_description(best);
+
+            if (sawmon) /* could already see monster */
+                pline("%s %s to shine %s.", Yname2(best),
+                      otense(best, "begin"), adesc);
+            else if (canseemon(mon)) /* didn't see it until new light */
+                pline("%s %s shining %s.", Yname2(best),
+                      otense(best, "are"), adesc);
+            else if (sawloc) /* saw location but not invisible monster */
+                pline("%s begins to shine %s.", Something, adesc);
+            else /* didn't see location until new light */
+                pline("%s is shining %s.", Something, adesc);
+        }
+    }
     update_mon_intrinsics(mon, best, TRUE, creation);
     /* if couldn't see it but now can, or vice versa, */
-    if (!creation && (unseen ^ !canseemon(mon))) {
+    if (!creation && (sawmon ^ !canseemon(mon))) {
         if (mon->minvis && !See_invisible) {
             pline("Suddenly you cannot see %s.", nambuf);
             makeknown(best->otyp);
-        } /* else if (!mon->minvis) pline("%s suddenly appears!",
-             Amonnam(mon)); */
+        } /* else if (!mon->minvis)
+           *     pline("%s suddenly appears!", Amonnam(mon)); */
     }
 }
 #undef RACE_EXCEPTION
@@ -1057,6 +1085,11 @@ extract_from_minvent(
         impossible("extract_from_minvent called on object not in minvent");
         return;
     }
+    /* handle gold dragon scales/scale-mail (lit when worn) before clearing
+       obj->owornmask because artifact_light() expects that to be W_ARM */
+    if ((unwornmask & W_ARM) != 0 && obj->lamplit && artifact_light(obj))
+        end_burn(obj, FALSE);
+
     obj_extract_self(obj);
     obj->owornmask = 0L;
     if (unwornmask) {