Glibc 2.31 porting notes/stime removal

From the release notes:

* The obsolete function stime is no longer available to newly linked
  binaries, and its declaration has been removed from <time.h>.
  Programs that set the system time should use clock_settime instead.

Also note something which you may want to fix while in the area:

* We plan to remove the obsolete function ftime, and the header
  <sys/timeb.h>, in a future version of glibc.  In this release, the
  header still exists but calling ftime will cause a compiler warning.
  All programs should use gettimeofday or clock_gettime instead.

Man pages:

• stime (old)
• clock_settime (new)

Examples:

• "net-misc/getdate-1.2-r1 : getdate.c:(.text.startup+<snip>): undefined reference to stime". bug #709642