autogen.sh now arranges for git to check hashes

Suggested by Karl Fogel in:
http://lists.gnu.org/archive/html/emacs-devel/2016-01/msg01802.html
* autogen.sh: Do "git config transfer.fsckObjects true".

autogen.sh

@@ -220,6 +220,11 @@ echo timestamp > src/stamp-h.in || exit
 ## Configure Git, if using Git.
 if test -d .git && (git status -s) >/dev/null 2>&1; then
 
+    # Check hashes when transferring objects among repositories.
+
+    git config transfer.fsckObjects true || exit
+
+
     # Configure 'git diff' hunk header format.
 
     git config 'diff.elisp.xfuncname' \