Reintroduce -fstack-protector

Reintroduce -fstack-protector

We removed this previously due to build failures in:

  commit 14ac764ec86452ca607403f314b0f8355d80290c
  Author: David Herrmann <dh.herrmann@gmail.com>
  Date:   Mon Sep 9 16:03:41 2013 +0200

      build: remove -fstack-protector

Reintroduce it but this time disable it if it's not supported. We use the
CC-flags testing to prevent build-failures on gcc without libssp support.

Cc: Giovanni Campagna <gcampagn@redhat.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>