mod_ssl: Ensure that the SSL close notify alert is flushed to the client.
         PR54998.

Submitted By: Tim Kosse <tim.kosse filezilla-project.org>, ylavic
Committed By: ylavic


mod_ssl: SSL_smart_shutdown(): follow up to r1601184.
Use SSL_get_wbio() to comply with OPENSSL_NO_SSL_INTERN.
Stop SSL shutdown loop when flush fails.


mpm_event[opt]: Send the SSL close notify alert when the KeepAliveTimeout
                expires. PR54998.

Submitted by: ylavic
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1651077 13f79535-47bb-0310-9956-ffa450edef68