Fix for QUOTE() function.

mysql-test/r/func_str.result

@@ -170,6 +170,9 @@ quote(concat('abc\'', '\\cba'))
 select quote(1/0), quote('\0\Z');
 quote(1/0)	quote('\0\Z')
 NULL	'\0\Z'
+select length(quote(concat(char(0), "test")));
+length(quote(concat(char(0), "test")))
+8
 select reverse("");
 reverse("")
 

mysql-test/t/func_str.test

@@ -69,7 +69,7 @@ select decode(encode("abcdef","monty"),"monty")="abcdef";
 select quote('\'\"\\test');
 select quote(concat('abc\'', '\\cba'));
 select quote(1/0), quote('\0\Z');
-
+select length(quote(concat(char(0), "test")));
 #
 # Wrong usage of functions
 #

sql/item_strfunc.cc

@@ -2398,7 +2398,7 @@ String *Item_func_quote::val_str(String *str)
   */
   to= (char*) str->ptr() + new_length - 1;
   *to--= '\'';
-  for (start= (char*) arg->ptr() ; end-- != start; to--)
+  for (start= (char*) arg->ptr(),end= start + arg_length; end-- != start; to--)
   {
     /*
       We can't use the bitmask here as we want to replace \O and ^Z with 0