Portability fix.
Portability fix.


sql/sql_lex.h:
  LEX::requires_prelocking():
    Portability fix. Seems that VC++ does not understand implicit pointer
    to bool conversion.

davidl-zend/zenddbi,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,ollie314/server,slanterns/server,davidl-zend/zenddbi,natsys/mariadb_10.2,natsys/mariadb_10.2,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,davidl-zend/zenddbi,davidl-zend/zenddbi,ollie314/server,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,ollie314/server,natsys/mariadb_10.2,ollie314/server,davidl-zend/zenddbi