Work around a bug in both the Linux and SunOS 64-bit kernels:

Work around a bug in both the Linux and SunOS 64-bit kernels:
nanosleep mishandles sleeps for longer than 2**31 seconds.
Problem reported by Frank v Waveren in
<http://lists.gnu.org/archive/html/bug-coreutils/2006-08/msg00298.html>.
* lib/nanosleep.c (BILLION): New constant.
(getnow) [HAVE_BUG_BIG_NANOSLEEP]: New functions.
(rpl_nanosleep) [HAVE_BUG_BIG_NANOSLEEP]: Completely new implementation.
* m4/nanosleep.m4 (gl_FUNC_NANOSLEEP): Require gl_CLOCK_TIME.
* modules/nanosleep (Depends-on): Add gettime.