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 = '_';

src/util/string.hpp

@@ -244,7 +244,7 @@ inline String uncanonical_name_form(String s) {
 }
 
 /// Convert a field name to canonical form, then to lower case, then trim it
-String unified_form(String&);
+String unified_form(String);
 
 /// Convert a field name to a string that can be shown to the user
 String name_to_caption(const String&);