Create an 1.3.x backport branch for r1902208 and r1902304:
- r1902208: Add support for BIO_CTRL_EOF, which is being used by OpenSSL 3.0+
  and OpenSSL 1.1.1e.
- r1902304: Fix the return value for unknown controls in the BIO control
  functions.


git-svn-id: https://svn.apache.org/repos/asf/serf/branches/1.3.x-r1902208+r1902304@1909396 13f79535-47bb-0310-9956-ffa450edef68