Initial part of WL#5047, which is about transforming SQL execution into an object hierarchy with methods for preparation and execution. The existing Sql_statement class (defined in sql_lex.h) will be modified as follows: - The class is renamed to Sql_cmd so that it is not confused with Statement and Prepared_statement. - Remove the m_lex member from the base class (it should not be necessary, and the LEX object should eventually go away. - Add a method sql_command_code() that is used to access the legacy SQL command code of the statement. The Sql_cmd class, including the enum_sql_command definition, is put into a separate file sql/sql_cmd.h. No HLS is required for this WL.
New methods on Sql_cmd: virtual enum_sql_command sql_command_code() const; This method will be implemented for each derived class of Sql_cmd to return the legacy SQL command code associated with the statement.