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

build-aux/.cvsignore

@@ -13,4 +13,7 @@ link-warning.h
 mdate-sh
 missing
 texinfo.tex
+update-copyright
+useless-if-before-free
+vc-list-files
 ylwrap

build-aux/.gitignore

@@ -13,4 +13,7 @@
 /mdate-sh
 /missing
 /texinfo.tex
+/update-copyright
+/useless-if-before-free
+/vc-list-files
 /ylwrap