Don't give warnings for empty statements with comments

@appendixsubsec Changes in release 3.23.49

@itemize @bullet

@item

Don't give warning for statement that is only a comment;  This is needed for

@code{mysqldump --disable-keys} to work.

@item

Fixed unlikely caching bug when doing a join without keys. In this case

the last used field for a table always returned @code{NULL}.

@item

select 1+2/*hello*/+3;

select 1 /* long

multi line comment */;

!$1065 /* empty query */;

!$1065 ;

select 1 /*!32301 +1 */;

select 1 /*!52301 +1 */;

select 1--1;

+1;

select 1 # The rest of the row will be ignored

;

/* line with only comment */;

#define OPTION_LOW_PRIORITY_UPDATES	8192

#define OPTION_WARNINGS		16384

#define OPTION_AUTO_IS_NULL	32768

#define OPTION_SAFE_UPDATES	65536L*2

#define OPTION_FOUND_COMMENT	65536L

#define OPTION_SAFE_UPDATES	OPTION_FOUND_COMMENT*2

#define OPTION_BUFFER_RESULT	OPTION_SAFE_UPDATES*2

#define OPTION_BIN_LOG          OPTION_BUFFER_RESULT*2

#define OPTION_NOT_AUTO_COMMIT	OPTION_BIN_LOG*2

      return(TEXT_STRING);

    case STATE_COMMENT:			//  Comment

      lex->options|= OPTION_FOUND_COMMENT;

      while ((c = yyGet()) != '\n' && c) ;

      yyUnget();			// Safety against eof

      state = STATE_START;		// Try again

	break;

      }

      yySkip();				// Skip '*'

      lex->options|= OPTION_FOUND_COMMENT;

      if (yyPeek() == '!')		// MySQL command in comment

      {

	ulong version=MYSQL_VERSION_ID;

  SQLCOM_BEGIN, SQLCOM_LOAD_MASTER_TABLE, SQLCOM_CHANGE_MASTER,

  SQLCOM_RENAME_TABLE, SQLCOM_BACKUP_TABLE, SQLCOM_RESTORE_TABLE,

  SQLCOM_RESET, SQLCOM_PURGE, SQLCOM_SHOW_BINLOGS,

  SQLCOM_SHOW_OPEN_TABLES, SQLCOM_DO,

  SQLCOM_SHOW_OPEN_TABLES, SQLCOM_DO, SQLCOM_EMPTY_QUERY,

  SQLCOM_END

};