Strict mode now gives error if one tries to update a virtual column.

mysql-test/suite/vcol/r/vcol_column_def_options_innodb.result:
  Updated test results
mysql-test/suite/vcol/r/vcol_column_def_options_myisam.result:
  Updated test results
mysql-test/suite/vcol/r/vcol_keys_innodb.result:
  Updated test results
mysql-test/suite/vcol/r/vcol_keys_myisam.result:
  Updated test results
mysql-test/suite/vcol/r/vcol_misc.result:
  Added new test for 'show columns' and error handling when trying to update a virtual column.
mysql-test/suite/vcol/t/vcol_misc.test:
  Added new test for 'show columns' and error handling when trying to update a virtual column.
sql/sql_base.cc:
  Strict mode now gives error if one tries to update a virtual column.
sql/sql_show.cc:
  Show PERSISTENT instead of VIRTUAL for persistent columns.

There was no error thrown when creating a table with a virtual table
computed by an expression returning a row.
This caused a crash when inserting into the table.

Removed periods at the end of the error messages for virtual columns.
Adjusted output in test result files accordingly. 

The original patch has been ameliorated by Sanja and Igor.