Patch license update to developer's FAQ

I have added to the developer's FAQ that we don't want
non-BSD-compatible licensed patches:
   <li>PostgreSQL is licensed under a BSD license.  By posting a patch   to the public PostgreSQL mailling lists, you
aregiving the PostgreSQL   Global Development Group the non-revokable right to distribute your   patch under the BSD
license. If you use code that is available under   a BSD-compatible license (eg. public domain), please note that in
your  email submission.  If the license is not BSD-compatible (e.g. GPL),   please do not post the patch.</li>
 

--  Bruce Momjian  <bruce@momjian.us>          http://momjian.us EnterpriseDB
http://www.enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +