use vector<string_pair> instead of map<string, string>

src/helpers.cpp

@@ -180,6 +180,15 @@ bool CaseInsensitiveSorting::operator()(string a, string b)
 	return a < b;
 }
 
+bool CaseInsensitiveSorting::operator()(const string_pair &a, const string_pair &b)
+{
+	string aa = a.first;
+	string bb = b.first;
+	ToLower(aa);
+	ToLower(bb);
+	return aa < bb;
+}
+
 bool CaseInsensitiveSorting::operator()(Song *sa, Song *sb)
 {
 	string a = sa->GetName();