Run "make update-copyright" and then...
* gnulib: Update to latest with copyright year adjusted.
* tests/init.sh: Sync with gnulib to pick up copyright year.
* bootstrap: Likewise.
* doc/grep.in.1: Use "-" in copyright year ranges, not \en.
Update Gnulib to latest. Also:
* src/dfasearch.c (EGexecute): Use ptrdiff_t, not size_t,
to match new Gnulib API.
* tests/Makefile.am (TESTS): Add dfa-invalid-utf8.
* tests/dfa-invalid-utf8: New file.