localize card links, add_link, remove_links

src/util/string.cpp

@@ -137,7 +137,7 @@ void uncanonical_name_form_in_place(String& str) {
   }
 }
 
-String unified_form(String& str) {
+String unified_form(String str) {
   str = trim(str);
   for (String::iterator it = str.begin(); it != str.end(); ++it) {
     if (*it == ' ') *it = '_';