autotools: default to -Wvla -std=gnu11
autotools: default to -Wvla -std=gnu11

We can't really support anything less than gcc-4.8 anyway.

Signed-off-by: Christian Brauner <48455ab3070520a2d174545c7239d6d0fabd9a83@ubuntu.com>

ss1h2a3tw/lxc,caglar10ur/lxc,caglar10ur/lxc,hallyn/lxc,hallyn/lxc,ss1h2a3tw/lxc,caglar10ur/lxc,ss1h2a3tw/lxc,hallyn/lxc