util: fix crash converting an invalid future date to string
Post-2038 timestamps cannot be handled on 32-bit architectures. Clamp
such dates to the maximum 32-bit timestamp.
$ "$TESTDIR/hghave" inotify || exit 80
$ hg init
$ echo "[extensions]" > .hg/hgrc
$ echo "inotify=" >> .hg/hgrc
$ hg inserve -d --pid-file .hg/inotify.pid
$ echo a > a
$ hg ci -Aqm0
$ hg co -q null
$ hg co -q
$ hg st
$ cat a
a
$ kill `cat .hg/inotify.pid`