Bug #21793 Missing CF_CHANGES_DATA and CF_STATUS_COMMAND for 
           handful of commands

CF_CHANGES_DATA and CF_STATUS_COMMAND flags added to the 
commands mentioned in the bug description. With the following
two exceptions: 

1) 4 commands do not exist: 
SQLCOM_RENAME_DB
SQLCOM_LOAD_MASTER_DATA
SQLCOM_LOAD_MASTER_TABLE
SQLCOM_SHOW_COLUMN_TYPES

2) All SQLCOM_SHOW_* commands already had CF_STATUS_COMMAND,
leaving only SQLCOM_BINLOG_BASE64_EVENT.

Further, check_prepared_statement() in sql_prepare.cc has been
simplified by taking advantage of the CF_STATUS_COMMAND flag.

Note that no test case has been added.