buildroot

postgresql: security bump to 9.6.7

from https://www.postgresql.org/about/news/1829/

Fixes:
[1] CVE-2018-1052: Fix the processing of partition keys containing multiple
                   expressions

[2] CVE-2018-1053: Ensure that all temporary files made with "pg_upgrade" are
                   non-world-readable

Signed-off-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>