Revision 1902208

Add support for BIO_CTRL_EOF and implement the hit eof logic for ssl buckets
and APR files.

Potentially OpenSSL can check BIOs for EOF. For example, OpenSSL 1.1.1e [1] and
OpenSSL 3.0+ [2] have such checks.

[1] https://github.com/openssl/openssl/commit/db943f43a60d1b5b1277e4b5317e8f288e7a0a3a
[2] https://github.com/openssl/openssl/commit/d924dbf4ae127c68463bcbece04b6e06abc58928

Patch by: Denis Kovalchuk <denis.kovalchuk{_AT_}visualsvn.com>

* buckets/ssl_buckets.c
  (serf_ssl_context_t): New hit_eof variable.
  (bio_bucket_read): Properly set the hit_eof variable.
  (bio_bucket_ctrl): Rework to support BIO_CTRL_EOF.
  (bio_file_ctrl): New ctrl function for APR files to support BIO_CTRL_EOF.
  (bio_file_method,
   bio_meth_file_new): Use the new bio_file_ctrl().
  (ssl_init_context): Init the hit_eof variable.

* test/MockHTTPinC/MockHTTP_server.c
  (sslCtx_t): New hit_eof variable.
  (bio_apr_socket_ctrl): Rework to support BIO_CTRL_EOF.
  (bio_apr_socket_read): Properly set the hit_eof variable.
  (initSSLCtx): Init the hit_eof variable.