Fix class members getting misoptimized away.

src/V3Dead.cpp

@@ -328,6 +328,7 @@ private:
     bool mightElimVar(AstVar* nodep) {
         return (!nodep->isSigPublic()  // Can't elim publics!
                 && !nodep->isIO()
+                && !nodep->isClassMember()
                 && ((nodep->isTemp() && !nodep->isTrace())
                     || (nodep->isParam() && !nodep->isTrace() && !v3Global.opt.xmlOnly())
                     || m_elimUserVars));  // Post-Trace can kill most anything