old bug report: unchanging iron golem still rehumanizes

Calling rehumanize directly when u.mh > 0 doesn't consider Unchanging
(perhaps it should?).  But, it's probably better to call losehp anyway.
Also, part of a buglist item: .5PD didn't affect rust trap damage on iron golem

doc/fixes34.3

@@ -63,6 +63,7 @@ allow a crystal ball to detect mimics via ']'
 prevent boulder option from accepting a symbol that matches a monster symbol
 traveling while standing on a trap would sometime step in the wrong direction
 avoid traveling into water/lava, using usual running rules
+unchanging iron golem would still rehumanize in a rust trap
 
 
 Platform- and/or Interface-Specific Fixes

src/trap.c

@@ -779,9 +779,12 @@ unsigned trflags;
 	    case RUST_TRAP:
 		seetrap(trap);
 		if (u.umonnum == PM_IRON_GOLEM) {
+		    int dam = u.mhmax;
+
 		    pline("%s you!", A_gush_of_water_hits);
 		    You("are covered with rust!");
-		    rehumanize();
+		    if (Half_physical_damage) dam = (dam+1) / 2;
+		    losehp(dam, "rusting away", KILLED_BY);
 		    break;
 		} else if (u.umonnum == PM_GREMLIN && rn2(3)) {
 		    pline("%s you!", A_gush_of_water_hits);