BUG#9535 Warning for "create table t as select uuid();"

- Set max_length of Item_func_uuid to max_length*system_charset_info->mbmaxlen
    Note! Item_func_uuid should be set to use 'ascii' charset when hex(), format(), md5()
etc will use 'ascii'
    - Comitting again, the old patch seems to have been lost.

mysql-test/t/func_misc.test

@@ -38,4 +38,9 @@ select a from t1 where mid(a+0,6,3) = ( mid(20040106123400,6,3) );
 
 drop table t1;
 
+# Test for BUG#9535
+create table t1 as select uuid(), length(uuid());
+show create table t1;
+drop table t1;
+
 # End of 4.1 tests