pyrolisk feedback

From a report 9 years ago, a pet pyrolisk was repeatedly gazing at a
grey-elf and nothing happened.  It turned out that the elf was wearing
an elven cloak which was negating damage some of the time (most of the
time back then) but with no indication that that's what was happening.

This makes many types of damage that are negated by MC say so.
Probably other types of damage should do likewise.

src/mhitm.c

@@ -967,7 +967,8 @@ mdamagem(struct monst *magr, struct monst *mdef,
     if (!mhm.damage)
         return mhm.hitflags;
 
-    if ((mdef->mhp -= mhm.damage) < 1) {
+    mdef->mhp -= mhm.damage;
+    if (mdef->mhp < 1) {
         if (m_at(mdef->mx, mdef->my) == magr) { /* see gulpmm() */
             remove_monster(mdef->mx, mdef->my);
             mdef->mhp = 1; /* otherwise place_monster will complain */