Move Lexer to u16string handling, for unicode support

src/Evaluator/BinaryEvaluation.cpp

@@ -96,7 +96,7 @@ shared_ptr<BooleanEvalValue> Evaluator::EvaluateBooleanBinary(const BoundBinaryE
 shared_ptr<StringEvalValue> Evaluator::EvaluateStringBinary(const BoundBinaryExpression* expression){
     if (expression->GetOperation() != BoundBinaryOperation::Concatenation)
         throw;
-    std::ostringstream strs;
+    std::basic_ostringstream<char16_t > strs;
     auto left = this -> EvaluateStringExpression(expression->GetLeft());
     strs << *left->EvaluateString();
     auto right = this -> EvaluateExpression(expression->GetRight());