CLEANUP: ssl: move all BIO_* definitions to openssl-compat

CLEANUP: ssl: move all BIO_* definitions to openssl-compat

The following macros are now defined for openssl < 1.1 so that we
can remove the code performing direct access to the structures :

  BIO_get_data(), BIO_set_data(), BIO_set_init(), BIO_meth_free(),
  BIO_meth_new(), BIO_meth_set_gets(), BIO_meth_set_puts(),
  BIO_meth_set_read(), BIO_meth_set_write(), BIO_meth_set_create(),
  BIO_meth_set_ctrl(), BIO_meth_set_destroy()