Work after 2038 on 32-bit GNU/Linux

This adds support for 64-bit time_t on 32-bit GNU/Linux ARM and
x86, where time_t was historically 32-bit.  The resulting Emacs
should continue to work for timestamps after mid-January 2038.
* admin/merge-gnulib (GNULIB_MODULES): Add year2038.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.

admin/merge-gnulib

@@ -48,7 +48,7 @@ GNULIB_MODULES='
   stpcpy strnlen strtoimax symlink sys_stat sys_time
   tempname time-h time_r time_rz timegm timer-time timespec-add timespec-sub
   update-copyright unlocked-io utimensat
-  vla warnings
+  vla warnings year2038
 '
 
 AVOIDED_MODULES='

lib/gnulib.mk.in

@@ -167,7 +167,8 @@
 #  update-copyright \
 #  utimensat \
 #  vla \
-#  warnings
+#  warnings \
+#  year2038
 
 
 MOSTLYCLEANFILES += core *.stackdump

m4/gnulib-comp.m4

@@ -210,6 +210,8 @@ AC_DEFUN([gl_EARLY],
   # Code from module vla:
   # Code from module warnings:
   # Code from module xalloc-oversized:
+  # Code from module year2038:
+  AC_REQUIRE([AC_SYS_YEAR2038])
 ])
 
 # This macro should be invoked from ./configure.ac, in the section