ddressing some cppcheck warnings. yes this will be cleaned up in a

following commit. tests pass.

util/ExpressionParser.rl

@@ -152,7 +152,7 @@ bool HS_CDECL readExpression(const std::string &input, std::string &expr,
     UNUSED const char *eof = pe;
     UNUSED const char *ts = p, *te = p;
     int cs;
-    UNUSED int act;
+    //UNUSED int act;
 
     assert(p);
     assert(pe);

util/ng_corpus_generator.h

@@ -47,7 +47,7 @@ class NGHolder;
 } // namespace ue2
 
 struct CorpusGenerationFailure {
-    explicit CorpusGenerationFailure(const std::string s) :
+    explicit CorpusGenerationFailure(const std::string& s) :
         message(std::move(s)) {}
     std::string message;
 };