* m4/year2038.m4 (gl_YEAR2038_TEST_INCLUDES): Check that time_t
can go to 2**32 - 1, not to 2**63 - 1, as the former is enough to
be year 2038 safe. Unsigned 32-bit time_t (AmigaOS) and signed
40-bit time_t (Unisys ClearPath) have occurred in the wild, and
even if Gnulib code is rarely or never ported to them there’s no
need to exclude them merely because of year 2038 issues.
(gl_YEAR2038_BODY): Adjust messages to match. Use 2**32 - 1,
not 2**32, as the test timestamp, to allow unsigned 32-bit time_t.