Update nettle to 2.7.1 and switch to release tarball.
Update nettle to 2.7.1 and switch to release tarball.

We no longer need any patches on nettle, so use the upstream release
directly.

shoreflyer/cerbero,centricular/cerbero,multipath-rtp/cerbero,AlertMe/cerbero,lubosz/cerbero,fluendo/cerbero,nirbheek/cerbero,fluendo/cerbero,ramaxlo/cerbero,flexVDI/cerbero,sdroege/cerbero,sdroege/cerbero,fluendo/cerbero,ylatuya/cerbero,ford-prefect/cerbero,ramaxlo/cerbero,brion/cerbero,nzjrs/cerbero,multipath-rtp/cerbero,flexVDI/cerbero,AlertMe/cerbero,ford-prefect/cerbero,flexVDI/cerbero,justinjoy/cerbero,EricssonResearch/cerbero,nzjrs/cerbero,atsushieno/cerbero,shoreflyer/cerbero,nirbheek/cerbero-old,brion/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,ramaxlo/cerbero,ylatuya/cerbero,GStreamer/cerbero,brion/cerbero,sdroege/cerbero,centricular/cerbero,EricssonResearch/cerbero,ikonst/cerbero,fluendo/cerbero,nzjrs/cerbero,nirbheek/cerbero-old,ikonst/cerbero,OptoFidelity/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,lubosz/cerbero,superdump/cerbero,sdroege/cerbero,lubosz/cerbero,ford-prefect/cerbero,nirbheek/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,GStreamer/cerbero,jackjansen/cerbero,atsushieno/cerbero,ylatuya/cerbero,AlertMe/cerbero,shoreflyer/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,davibe/cerbero,nirbheek/cerbero-old,GStreamer/cerbero,ford-prefect/cerbero,flexVDI/cerbero,shoreflyer/cerbero,justinjoy/cerbero,brion/cerbero,AlertMe/cerbero,OptoFidelity/cerbero,ramaxlo/cerbero,justinjoy/cerbero,davibe/cerbero,shoreflyer/cerbero,nirbheek/cerbero-old,EricssonResearch/cerbero,jackjansen/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,ikonst/cerbero,davibe/cerbero,nzjrs/cerbero,flexVDI/cerbero,sdroege/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,davibe/cerbero,nirbheek/cerbero,jackjansen/cerbero,ikonst/cerbero,nirbheek/cerbero,justinjoy/cerbero,EricssonResearch/cerbero,centricular/cerbero,superdump/cerbero,atsushieno/cerbero,ikonst/cerbero,OptoFidelity/cerbero,jackjansen/cerbero,ylatuya/cerbero,lubosz/cerbero,GStreamer/cerbero,freedesktop-unofficial-mirror/gstreamer__sdk__cerbero,OptoFidelity/cerbero,GStreamer/cerbero,multipath-rtp/cerbero,multipath-rtp/cerbero,EricssonResearch/cerbero,ramaxlo/cerbero,fluendo/cerbero,superdump/cerbero,brion/cerbero,atsushieno/cerbero,centricular/cerbero,nzjrs/cerbero,AlertMe/cerbero,superdump/cerbero,freedesktop-unofficial-mirror/gstreamer__cerbero,multipath-rtp/cerbero,centricular/cerbero,atsushieno/cerbero