Revision 1775257

Get rid of another SSL feature check based on a version number.

* SConstruct: Add a check for OpenSSL ALPN support and provide
   SERF_HAVE_OPENSSL_ALPN.

* buckets/ssl_buckets.c:
  (serf_ssl_negotiate_protocol, ssl_get_selected_protocol): Use
   SERF_HAVE_OPENSSL_ALPN instead of OPENSSL_VERSION_NUMBER.

Found by: brane