Bug#805497: update libseccomp build-depends

[Daniel Baumann]

On 11/18/2015 09:22 PM, Michael Biebl wrote:
> Unfortunately, bumping the build-depends on
> libseccomp-dev has no effect. The generated dependency on libseccomp2
> would still be the same.

True, but when building systemd on a system with too old libseccomp,
e.g. when backporting systemd to jessie, it FTBFS.

Bumping the version on the libseccomp build-depends at least fixes this
(by making it visible that the there's also a libseccomp backport
required in order to build systemd).

Regards,
Daniel