BUG#11316: mysqltest, problems when assigning value with '#' to $variable

- Add stricter checking of syntax in mysqltest

mysql-test/t/rpl_loaddata.test

@@ -123,7 +123,7 @@ connection master;
 reset master;
 create table t2 (day date,id int(9),category enum('a','b','c'),name varchar(60),
 unique(day));
---error 1062;
+--error 1062
 load data infile '../../std_data/rpl_loaddata2.dat' into table t2 fields
 terminated by ',' optionally enclosed by '%' escaped by '@' lines terminated by
 '\n##\n' starting by '>' ignore 1 lines;