Internals: More const. No functional change intended.

src/V3Broken.cpp

@@ -343,8 +343,8 @@ void V3Broken::brokenAll(AstNetlist* nodep) {
         UINFO(1, "Broken called under broken, skipping recursion.\n");  // LCOV_EXCL_LINE
     } else {
         inBroken = true;
-        BrokenMarkVisitor mvisitor{nodep};
-        BrokenCheckVisitor cvisitor{nodep};
+        const BrokenMarkVisitor mvisitor{nodep};
+        const BrokenCheckVisitor cvisitor{nodep};
         s_allocTable.checkForLeaks();
         s_linkableTable.clear();
         s_brokenCntGlobal.inc();