postgresql: Security Advisory-postgresql-CVE-2016-0766

add CVE-2016-0766 patch for avoiding attackers to gain privileges
via unspecified vectors.
Patch comes from:
http://git.postgresql.org/gitweb/?p=postgresql.git;a=summary


commit f4aa3a18a20d51575562520754aa376b3b08b2d0

Signed-off-by: Zhixiong Chi <Zhixiong.Chi@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>