Give dragon armor extra effects

Dragon scales and dragon scale mails will provide some extra effects
when worn:

 - blue:   very fast speed
 - black:  level-drain resistance
 - green:  sickness resistance
 - gold:   hallucination resistance
 - orange: free action
 - red:    infravision
 - white:  slow digestion
 - yellow: stoning resistance

gray and silver don't have extra effects - those two are already the
best ones, so don't need any.

doc/fixes37.0

@@ -717,6 +717,7 @@ mark some messages as urgent ("You die*.", having equipment stolen, being
 if a leashed pet changed name (#name m) or an unnamed pet changed type
 	(polymorph or grow-up) and perm_invent was On, persistent inventory
 	display didn't get updated to show the leash's changed information
+give some dragon armor extra effects when worn
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

include/youprop.h

@@ -66,7 +66,8 @@
 
 /* Intrinsics only */
 #define HSick_resistance u.uprops[SICK_RES].intrinsic
-#define Sick_resistance (HSick_resistance || defends(AD_DISE, uwep))
+#define ESick_resistance u.uprops[SICK_RES].extrinsic
+#define Sick_resistance (HSick_resistance || ESick_resistance || defends(AD_DISE, uwep))
 
 #define Invulnerable u.uprops[INVULNERABLE].intrinsic /* [Tom] */
 

src/do_wear.c

@@ -30,6 +30,7 @@ static int Gloves_on(void);
 static void wielding_corpse(struct obj *, boolean);
 static int Shield_on(void);
 static int Shirt_on(void);
+static void dragon_armor_handling(struct obj *, boolean);
 static void Amulet_on(void);
 static void learnring(struct obj *, boolean);
 static void Ring_off_or_gone(struct obj *, boolean);
@@ -691,16 +692,100 @@ Shirt_off(void)
     return 0;
 }
 
+/* handle extra abilities for hero wearing dragon scale armor */
+static void
+dragon_armor_handling(struct obj *otmp, boolean puton)
+{
+    if (!otmp)
+        return;
+
+    switch (otmp->otyp) {
+        /* grey: no extra effect */
+        /* silver: no extra effect */
+    case BLACK_DRAGON_SCALES:
+    case BLACK_DRAGON_SCALE_MAIL:
+        if (puton) {
+            EDrain_resistance |= W_ARM;
+        } else {
+            EDrain_resistance &= ~W_ARM;
+        }
+        break;
+    case BLUE_DRAGON_SCALES:
+    case BLUE_DRAGON_SCALE_MAIL:
+        if (puton) {
+            if (!Very_fast)
+                pline("You speed up%s.", Fast ? " a bit more" : "");
+            EFast |= W_ARM;
+        } else {
+            EFast &= ~W_ARM;
+            if (!Very_fast && !g.context.takeoff.cancelled_don)
+                pline("You slow down.");
+        }
+        break;
+    case GREEN_DRAGON_SCALES:
+    case GREEN_DRAGON_SCALE_MAIL:
+        if (puton) {
+            ESick_resistance |= W_ARM;
+        } else {
+            ESick_resistance &= ~W_ARM;
+        }
+        break;
+    case RED_DRAGON_SCALES:
+    case RED_DRAGON_SCALE_MAIL:
+        if (puton) {
+            EInfravision |= W_ARM;
+        } else {
+            EInfravision &= ~W_ARM;
+        }
+        see_monsters();
+        break;
+    case GOLD_DRAGON_SCALES:
+    case GOLD_DRAGON_SCALE_MAIL:
+        (void) make_hallucinated((long) !puton,
+                                 g.program_state.restoring ? FALSE : TRUE,
+                                 W_ARM);
+        break;
+    case ORANGE_DRAGON_SCALES:
+    case ORANGE_DRAGON_SCALE_MAIL:
+        if (puton) {
+            Free_action |= W_ARM;
+        } else {
+            Free_action &= ~W_ARM;
+        }
+        break;
+    case YELLOW_DRAGON_SCALES:
+    case YELLOW_DRAGON_SCALE_MAIL:
+        if (puton) {
+            EStone_resistance |= W_ARM;
+        } else {
+            EStone_resistance &= ~W_ARM;
+        }
+        break;
+    case WHITE_DRAGON_SCALES:
+    case WHITE_DRAGON_SCALE_MAIL:
+        if (puton) {
+            ESlow_digestion |= W_ARM;
+        } else {
+            ESlow_digestion &= ~W_ARM;
+        }
+        break;
+    default:
+        break;
+    }
+}
+
 static int
 Armor_on(void)
 {
-    /*
-     * Gold DSM requires special handling since it emits light when worn.
-     */
     if (!uarm) /* no known instances of !uarm here but play it safe */
         return 0;
     uarm->known = 1; /* suit's +/- evident because of status line AC */
 
+    dragon_armor_handling(uarm, TRUE);
+
+    /*
+     * Gold DSM requires special handling since it emits light when worn.
+     */
     if (artifact_light(uarm) && !uarm->lamplit) {
         begin_burn(uarm, FALSE);
         if (!Blind)
@@ -721,6 +806,8 @@ Armor_off(void)
     setworn((struct obj *) 0, W_ARM);
     g.context.takeoff.cancelled_don = FALSE;
 
+    dragon_armor_handling(otmp, FALSE);
+
     if (was_arti_light && !artifact_light(otmp)) {
         end_burn(otmp, FALSE);
         if (!Blind)
@@ -745,6 +832,8 @@ Armor_gone(void)
     setnotworn(uarm);
     g.context.takeoff.cancelled_don = FALSE;
 
+    dragon_armor_handling(otmp, FALSE);
+
     if (was_arti_light && !artifact_light(otmp)) {
         end_burn(otmp, FALSE);
         if (!Blind)