*) mod_ssl: Handle SSL_read() return code 0 similarly to <0. It is needed

  *) mod_ssl: Handle SSL_read() return code 0 similarly to <0. It is needed
              when using OpenSSL 1.1.1 and should not harm for versions before
              1.1.1.
              Without the patch for 1.1.1 a 0 byte read no longer results in
              EAGAIN but instead in APR_EOF which leads to HTTP/2 failures.
              For the changelog: Fix HTTP/2 failures when using OpenSSL 1.1.1.
     trunk patch: http://svn.apache.org/r1843954
     2.4.x patch: svn merge -c 1843954 ^/httpd/httpd/trunk .
     +1: rjung, druggeri, rpluem

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1844047 13f79535-47bb-0310-9956-ffa450edef68