Work around man pages being rebuilt unnecessarily making distcheck fail

Add distcleancheck_listfiles to work around BSD make wanting to
rebuild to man pages even though they are in the source directory.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5494 d4fa192b-c00b-0410-8231-f00ffab90ce4

Makefile.am

@@ -21,3 +21,6 @@ distcheck-hook:
 	  exit 1 ; \
 	fi
 
+distcleancheck_listfiles = \
+	find . -type f -exec sh -c 'test -f $(srcdir)/$$1 || echo $$1' \
+		sh '{}' ';'