Fix some clang-tidy warnings

src/V3GraphDfa.cpp

@@ -193,7 +193,7 @@ private:
         return NULL;  // No match
     }
 
-    void findNfasWithInput(DfaVertex* dfaStatep, DfaInput input, DfaStates& nfasWithInput) {
+    void findNfasWithInput(DfaVertex* dfaStatep, const DfaInput& input, DfaStates& nfasWithInput) {
         // Return all NFA states, with the given input transition from
         // the nfa states a given dfa state was constructed from.
         nextStep();