* nscd/nscd_getpw_r.c (nscd_getpw_r): Consolidate writing of the
request with one writev call. Protect all read calls with
TEMP_FAILURE_RETRY.
* nscd/nscd_getgr_r.c (nscd_getgr_r): Likewise.
* nscd/nscd_gethst_r.c (nscd_gethst_r): Likewise.
* nscd/hstcache.c: Use extend_alloca to reallocate alloca'd buffer.
Protect writev calls with TEMP_FAILURE_RETRY.
* nscd/grpcache.c: Likewise.
* nscd/pwdcache.c: Likewise.