Port better to CentOS 5 Problems reported by Tom G. Christensen in: https://lists.gnu.org/r/bug-gnulib/2017-11/msg00053.html * doc/glibc-functions/strverscmp.texi (strverscmp): Document strverscmp bug with glibc 2.9 and earlier. * doc/posix-functions/tzset.texi (tzset): Document that TZ with angle brackets is POSIX-2001 and later. * tests/test-nstrftime.c: Include unistd.h. (TZ_ANGLE_BRACKETS_SHOULD_WORK): New macro. (TZ): Use it to skip tests with angle brackets in TZ, for older systems.