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:
   
PostgreSQL is licensed under a BSD license.  By posting a patch   to the public PostgreSQL mailling lists, you are giving 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.

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