Log Message:
-----------
Update release notes in "major" and "migration" sections. Still have
remainder of release notes to review.
Modified Files:
--------------
pgsql/doc/src/sgml:
release.sgml (r1.517 -> r1.518)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/release.sgml?r1=1.517&r2=1.518)