* nis/nss_nis/nis-netgrp.c: Remove locking by using data in struct
__netgrent object passed in instead of global variables.
Optimize.
* nis/nss_nisplus/nisplus-netgrp.c: Remove locking by using data
in struct __netgrent object passed in instead of global variables.
* inet/netgroup.h (struct __netgrent): Add service_user field.
Move cursor in anonymous union, add new field location to that
union.
* inet/getnetgrent_r.c: Extensive rewrite to really enable
concurrent uset of set/get/endnetgrent and innetgr.