database.

If a user has a right to update anything in the current database then the 
access was granted and further checks of access rights for underlying tables
wasn't done correctly. The check is done before a view is opened and thus no
check of access rights for underlying tables can be carried out.
This allows a user to update through a view a table from another database for
which he hasn't enough rights.

Now the mysql_update() and the mysql_test_update() functions are forces
re-checking of access rights after a view is opened.


mysql-test/t/grant.test:
  Added a test case for the bug#27878: Unchecked privileges on a view referring to a table from another database.
mysql-test/r/grant.result:
  Added a test case for the bug#27878: Unchecked privileges on a view referring to a table from another database.
sql/sql_update.cc:
  Bug#27878: Unchecked privileges on a view referring to a table from another 
  database.
  Now the mysql_update() function forces re-checking of access rights after 
  the view is opened.
sql/sql_prepare.cc:
  Bug#27878: Unchecked privileges on a view referring to a table from another 
  database.
  Now the mysql_test_update() function forces re-checking of access rights after
  the view is opened.