Move realms from the nation file into a new realms file:

Move realms from the nation file into a new realms file:
(boundstr, realmstr): Rename, new members ef_type, r_cnum, r_uid,
r_realm, r_timestamp.
(natstr): Remove member nat_b[].
(EF_REALM, realm_ca): New.
(empfile): Add it.
(ef_open_srv, ef_close_srv, main): Deal with new file.
(getrealm, putrealm): New.
(add, new, real, list_realm, sarg_getrange): Use them.