build: introduce git-version-gen
* .gitignore: Add .version.
* Makefile.am (EXTRA_DIST, BUILT_SOURCES): Add $(srcdir)/.version.
Add rules to check NEWS, generate $(srcdir)/.version and
$(distdir)/.tarball-version files.
Change ChangeLog and CREDITS generation rules to depend on
$(srcdir)/.version instead of $(srcdir)/.git/refs/heads/*.
* NEWS: Add dates to recent releases.
* configure.ac (AC_INIT): Use git-version-gen.
(AM_INIT_AUTOMAKE): Remove check-news.
* git-version-gen: Import from gnulib.
* make-dist: Check NEWS.
diff --git a/make-dist b/make-dist
index fb5d8ce..fffedfb 100755
--- a/make-dist
+++ b/make-dist
@@ -21,5 +21,6 @@
./configure --enable-maintainer-mode
make -s $j distcheck
+make -s $j news-check
mv -f strace-*.tar.xz ..