buildroot

libgcrypt: security bump to version 1.7.9

Fixes CVE-2017-0379: Mitigate a local side-channel attack on Curve25519
dubbed "May the Fourth be With You".

As we are close to release, don't update to the latest 1.8.1 version,
but to a maintenance release from the 1.7 branch.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
(cherry picked from commit cd4514109a6bd248d6ca7713d97e3b257ae91c6f)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>