* nis/nss_nis/nis-hosts.c: Make _nss_nis_endhostent an alias of
_nss_nis_sethostent. Work around the different prototypes.
* nis/nss_nis/nis-grp.c: Make _nss_nis_endgrent an alias of
_nss_nis_setgrent. Work around the different prototypes.
* nis/nss_nis/nis-ethers.c (internal_nis_endetherent): New
function. Split out from _nss_nis_endetherent.
(internal_nis_setetherent): Use internal_nis_endetherent instead of
duplicating the code.
* nis/nss_nis/nis-alias.c: Make _nss_nss_nis_endaliasent an alias
of _nss_nis_setaliasent.
* nis/nss_nis/nis-service.c (internal_nis_setservent): Reuse
internal_nis_endservent code, don't duplicate it.