Use Gnulib's `git-version-gen'.

* GUILE-VERSION (GUILE_VERSION): Remove.

* Makefile.am (dist-hook): Depend on `gen-tarball-version'.
  (BUILT_SOURCES): New variable.
  ($(top_srcdir)/.version, gen-tarball-version): New targets.

* cfg.mk (git-version-gen-tag-sed-script): New variable.

* configure.ac: Use `build-aux/git-version-gen' to generate the VERSION
  argument of `AC_INIT'.  Initialize Automake without `check-news'.
  Define $GUILE_VERSION as an alias for $PACKAGE_VERSION.

Makefile.am

@@ -43,7 +43,7 @@ DISTCLEANFILES = check-guile.log
 
 DISTCHECK_CONFIGURE_FLAGS = --enable-error-on-warning
 
-dist-hook: gen-ChangeLog
+dist-hook: gen-ChangeLog gen-tarball-version
 
 clean-local:
 	rm -rf cache/
@@ -60,4 +60,10 @@ gen-ChangeLog:
 	  mv $(distdir)/cl-t $(distdir)/ChangeLog;			\
 	fi
 
+BUILT_SOURCES = $(top_srcdir)/.version
+$(top_srcdir)/.version:
+	echo $(VERSION) > $@-t && mv $@-t $@
+gen-tarball-version:
+	echo $(VERSION) > $(distdir)/.tarball-version
+
 # Makefile.am ends here