- compilation error occured because of non portable code which
   assigned to ndb_socket_t::fd which is called
   ndb_socket_t::s on Windows in order to catch errors like
   this
 - fix by introducing new ndb_socket_create_from_native() function
   which can be used to create a ndb_socket_t from ndb_native_socket_t
   in a portable way without using #ifdefs.
 - also replace usages of SOCKET and int with ndb_native_socket_t