remove unused codes

Signed-off-by: Jack <jack.wgm@gmail.com>
improve ssl option

Signed-off-by: Jack <jack.wgm@gmail.com>
move include openssl header to ssl_stream.hpp

Signed-off-by: Jack <jack.wgm@gmail.com>
add socket_type description

Signed-off-by: Jack <jack.wgm@gmail.com>