maint: automate annual package-wide copyright-year update.

* .x-update-copyright: New.
* Makefile.am (EXTRA_DIST): Remove maint.mk.
* bootstrap.conf (gnulib_modules): Add maintainer-makefile and
update-copyright.  Remove gnumakefile, which is implied by
maintainer-makefile.
* cfg.mk (bootstrap-tools): Copy from old maint.mk.
* gnulib: Update.
* maint.mk: Remove, now copied from gnulib.
* examples/extexi: Add missing "(C)" in copyright statement so
update-copyright can recognize it.
* src/LR0.h: Likewise.
* src/print.h: Likewise.
* src/print_graph.h: Likewise.
* src/named-ref.c: Likewise.
* src/named-ref.h: Likewise.
* src/gram.c: Add missing comma in copyright statement.
* src/gram.h: Likewise.
(cherry picked from commit dbbb64f091)

Conflicts:

	Makefile.am
	gnulib
	maint.mk
	src/gram.h

lib/.gitignore

@@ -7,6 +7,7 @@
 /argmatch.c
 /argmatch.h
 /basename.c
+/bitrotate.h
 /c-ctype.c
 /c-ctype.h
 /c-strcase.h
@@ -33,6 +34,7 @@
 /getopt1.c
 /getopt_.h
 /getopt_int.h
+/getpagesize.c
 /gettext.h
 /gnulib.mk
 /hash.c
@@ -49,6 +51,7 @@
 /mbswidth.c
 /mbswidth.h
 /memchr.c
+/memchr.valgrind
 /obstack.c
 /obstack.h
 /pipe-safer.c