fix #H4142 - resistance from Excalibur

Enlightenment and end of game disclosure didn't report level-drain
resistance if that was obtained via wielding Excalibur (or Stormbringer
or Staff of Aesculapius).  Drain_resistance wasn't one of the attributes
set for intrinsics/extrinsics when wielding or unwielding weapon or
wearing/unwearing other equipment.  loseexp() checks resists_drli()
which does check for items in use, so level drain would be aborted,
possibly after messages claimed that it was taming place.  I didn't try
to untangle any of that, just changed set_artifact_intrinsic to include
a test for DRAIN_RES.

doc/fixes36.1

@@ -57,6 +57,8 @@ do not autopickup unpaid items in shops
 death due an unseen gas spore's explosion resulted in "killed by a died"
 allow optional parameter "true", "yes", "false", or "no" for boolean options
 actually make the castle chest not trapped
+level-drain resistance wasn't shown during enlightenment if it was conferred
+	by worn/wielded equipment
 
 
 Platform- and/or Interface-Specific Fixes

src/artifact.c

@@ -1,4 +1,4 @@
-/* NetHack 3.6	artifact.c	$NHDT-Date: 1446369462 2015/11/01 09:17:42 $  $NHDT-Branch: master $:$NHDT-Revision: 1.96 $ */
+/* NetHack 3.6	artifact.c	$NHDT-Date: 1451081581 2015/12/25 22:13:01 $  $NHDT-Branch: NetHack-3.6.0 $:$NHDT-Revision: 1.99 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -18,13 +18,12 @@ extern boolean notonhead; /* for long worms */
 #define get_artifact(o) \
     (((o) && (o)->oartifact) ? &artilist[(int) (o)->oartifact] : 0)
 
-STATIC_DCL boolean
+STATIC_DCL boolean FDECL(bane_applies, (const struct artifact *,
-FDECL(bane_applies, (const struct artifact *, struct monst *));
+                                        struct monst *));
 STATIC_DCL int FDECL(spec_applies, (const struct artifact *, struct monst *));
 STATIC_DCL int FDECL(arti_invoke, (struct obj *));
-STATIC_DCL boolean
+STATIC_DCL boolean FDECL(Mb_hit, (struct monst * magr, struct monst *mdef,
-FDECL(Mb_hit, (struct monst * magr, struct monst *mdef, struct obj *, int *,
+                                struct obj *, int *, int, BOOLEAN_P, char *));
-               int, BOOLEAN_P, char *));
 STATIC_DCL unsigned long FDECL(abil_to_spfx, (long *));
 STATIC_DCL uchar FDECL(abil_to_adtyp, (long *));
 STATIC_DCL boolean FDECL(untouchable, (struct obj *, BOOLEAN_P));
@@ -462,12 +461,13 @@ boolean being_worn;
  */
 void
 set_artifact_intrinsic(otmp, on, wp_mask)
-register struct obj *otmp;
+struct obj *otmp;
 boolean on;
 long wp_mask;
 {
     long *mask = 0;
-    register const struct artifact *oart = get_artifact(otmp);
+    register const struct artifact *art, *oart = get_artifact(otmp);
+    register struct obj *obj;
     register uchar dtyp;
     register long spfx;
 
@@ -489,19 +489,21 @@ long wp_mask;
         mask = &EDisint_resistance;
     else if (dtyp == AD_DRST)
         mask = &EPoison_resistance;
+    else if (dtyp == AD_DRLI)
+        mask = &EDrain_resistance;
 
     if (mask && wp_mask == W_ART && !on) {
-        /* find out if some other artifact also confers this intrinsic */
+        /* find out if some other artifact also confers this intrinsic;
-        /* if so, leave the mask alone */
+           if so, leave the mask alone */
-        register struct obj *obj;
+        for (obj = invent; obj; obj = obj->nobj) {
-        for (obj = invent; obj; obj = obj->nobj)
             if (obj != otmp && obj->oartifact) {
-                register const struct artifact *art = get_artifact(obj);
+                art = get_artifact(obj);
                 if (art->cary.adtyp == dtyp) {
                     mask = (long *) 0;
                     break;
                 }
             }
+        }
     }
     if (mask) {
         if (on)
@@ -514,10 +516,9 @@ long wp_mask;
     spfx = (wp_mask != W_ART) ? oart->spfx : oart->cspfx;
     if (spfx && wp_mask == W_ART && !on) {
         /* don't change any spfx also conferred by other artifacts */
-        register struct obj *obj;
         for (obj = invent; obj; obj = obj->nobj)
             if (obj != otmp && obj->oartifact) {
-                register const struct artifact *art = get_artifact(obj);
+                art = get_artifact(obj);
                 spfx &= ~art->cspfx;
             }
     }
@@ -1738,6 +1739,7 @@ long *abil;
         { &EAntimagic, AD_MAGM },
         { &EDisint_resistance, AD_DISN },
         { &EPoison_resistance, AD_DRST },
+        { &EDrain_resistance, AD_DRLI },
     };
     int k;
 
@@ -1792,7 +1794,6 @@ long *abil;
     long wornmask = (W_ARM | W_ARMC | W_ARMH | W_ARMS
                      | W_ARMG | W_ARMF | W_ARMU
                      | W_AMUL | W_RINGL | W_RINGR | W_TOOL
-                     /* [do W_ART and W_ARTI actually belong here?] */
                      | W_ART | W_ARTI);
 
     if (u.twoweap)
@@ -1808,7 +1809,9 @@ long *abil;
 
             if (art) {
                 if (dtyp) {
-                    if (art->cary.adtyp == dtyp || art->defn.adtyp == dtyp)
+                    if (art->cary.adtyp == dtyp /* carried */
+                        || (art->defn.adtyp == dtyp /* defends while worn */
+                            && (obj->owornmask & ~(W_ART | W_ARTI))))
                         return obj;
                 }
                 if (spfx) {