Update auxiliary maintainer mode build tools

* git-set-file-times: Update from rsync.
* git-version-gen: Update from gnulib.
* gitlog-to-changelog: Likewise.
diff --git a/git-set-file-times b/git-set-file-times
index 85d854e..077ac0e 100755
--- a/git-set-file-times
+++ b/git-set-file-times
@@ -1,5 +1,6 @@
-#!/usr/bin/perl -w
+#!/usr/bin/perl
 use strict;
+use warnings;
 
 # Sets mtime and atime of files to the latest commit time in git.
 #