media-libs/giflib-5.1.4 was marked stable on amd64 on 2016-11-19 and there are stable-on-amd64 packages such as dev-dotnet/libgdiplus-4.2-r2 which depend on it. However, stable-on-amd64 media-libs/libafterimage-1.20 continues to depend on <media-libs/giflib-5. Looks like that stabilisation request needs a bit more attention from our side.
Should be fine now - media-libs/libafterimage-1.20-r1, which does support giflib-5, is now stable on amd64.