Fix make dist infinite loop reported by Juan Manuel Guerrero at

<http://lists.gnu.org/archive/html/bug-bison/2008-01/msg00009.html>.
* .cvsignore: Add .version.
* .version.in: New.
* bootstrap.conf (gnulib_modules): Add git-version-gen.
* configure.ac (AC_CONFIG_FILES): Add .version.
* build-aux/.cvsignore: Add git-version-gen.

build-aux/.cvsignore

@@ -5,6 +5,7 @@ config.guess
 config.rpath
 config.sub
 depcomp
+git-version-gen
 install-sh
 javacomp.sh.in
 javaexec.sh.in