1003: Incorrect table name
in multi-table DELETE the set of tables to delete from actually 
references then tables in the other list, e.g:
DELETE alias_of_t1 FROM t1 alias_of_t1 WHERE ....
is a valid statement.
So we must turn off table name syntactical validity check for alias_of_t1 
because it's not a table name (even if it looks like one).
In order to do that we add a special flag (TL_OPTION_ALIAS) to 
disable the name checking for the aliases in multi-table DELETE.


mysql-test/r/delete.result:
  Bug #21392: multi-table delete with alias table name fails with
              1003: Incorrect table name
   - test case
mysql-test/t/delete.test:
  Bug #21392: multi-table delete with alias table name fails with
              1003: Incorrect table name
   - test case
sql/mysql_priv.h:
  Bug #21392: multi-table delete with alias table name fails with
              1003: Incorrect table name
   - add a special flag to disable the name checking for the aliases
     in multi-table DELETE
sql/sql_parse.cc:
  Bug #21392: multi-table delete with alias table name fails with
              1003: Incorrect table name
   - add a special flag to disable the name checking for the aliases
     in multi-table DELETE
sql/sql_yacc.yy:
  Bug #21392: multi-table delete with alias table name fails with
              1003: Incorrect table name
   - add a special flag to disable the name checking for the aliases
     in multi-table DELETE