GNU gethelp URI has changed

[Christophe Jarry]

Dear developers,

I found that several files inside GNU Autoconf used the URI
<http://www.gnu.org/gethelp> to redirect users that need help with GNU programs.

While this URI is still valid, it is in fact a redirection to
<http://www.gnu.org/help/gethelp.html>. I think it would be nice to change the
URI to point to the right location.

If you are ok with this change, I will send the patch to you on
<address@hidden>.

Christophe