Refactoring BIO: new socket-handling functions, deprecate older ones

Added functions:

BIO_socket
BIO_connect
BIO_listen
BIO_accept_ex
BIO_closesocket
BIO_sock_info

These get deprecated:

BIO_gethostbyname
BIO_get_port
BIO_get_host_ip
BIO_get_accept_socket
BIO_accept

Reviewed-by: Kurt Roeckx <kurt@openssl.org>