Windows build fix: init_once assignment needs to be casted (C99).
Windows build fix: init_once assignment needs to be casted (C99).

MariaDB/mariadb-connector-c,ottok/mariadb-connector-c,MariaDB/mariadb-connector-c,ottok/mariadb-connector-c,ottok/mariadb-connector-c,MariaDB/mariadb-connector-c