getgroups.2, gettimeofday.2, mincore.2, readv.2, stime.2, wait4.2, addseverity.3...

getgroups.2, gettimeofday.2, mincore.2, readv.2, stime.2, wait4.2, addseverity.3, adjtime.3, cfree.3, dysize.3, fgetgrent.3, fgetpwent.3, futimes.3, getdirentries.3, getgrent_r.3, getgrouplist.3, getmntent.3, getnetent_r.3, getprotoent_r.3, getpwent_r.3, getrpcent_r.3, getservent_r.3, getspnam.3, gsignal.3, initgroups.3, mkdtemp.3, on_exit.3, perror.3, psignal.3, putpwent.3, rcmd.3, rpmatch.3, setbuf.3, setnetgrent.3, sigvec.3, strsep.3, syslog.3, tempnam.3, termios.3, timegm.3, timeradd.3: Update FTM requirements (_DEFAULT_SOURCE)

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>