Move Lexer to u16string handling, for unicode support

src/Evaluator/EvalValues/StringEvalValue.hpp

@@ -9,10 +9,10 @@
 using namespace std;
 
 class StringEvalValue : public EvalValue{
-    string _value;
+    u16string _value;
     size_t _hash;
 public:
-    explicit StringEvalValue(string s){
+    explicit StringEvalValue(u16string s){
         _value = move(s);
         _hash = HashedString::ConstHash (_value.c_str());
     }
@@ -27,7 +27,7 @@ public:
         return this->_hash == b->GetHashCode();
     };
 
-    const string* EvaluateString() const final{
+    const u16string* EvaluateString() const final{
         return &_value;
     }
 
@@ -38,7 +38,7 @@ public:
     shared_ptr<EvalValue> IndexValue(EvalValue* val) final{
         // Porygon is 1-indexed, so we convert to that.
         auto l = val->EvaluateInteger() - 1;
-        return make_shared<StringEvalValue>(string(1, _value[l]));
+        return make_shared<StringEvalValue>(u16string(1, _value[l]));
     }
 
     std::size_t GetHashCode() final{