[glibc] Apply ubuntu 2.25.6. Contributes to JB#45152

Fixes CVE-2017-15670, CVE-2017-15671, CVE-2017-15804, CVE-2017-1000408,
CVE-2017-1000409, CVE-2017-16997.
Signed-off-by: Marko Saukko <marko.saukko@jolla.com>