It was merged into master 2 weeks ago, you probably run 18.06 not snapshot? https://downloads.openwrt.org/snapshots/packages/
Was just merged into master very close to the 18.06 release, so i wanted some feedback from master/snapshot users first. I made sure to have related packages available in 18.06, so it compiles against it and yes i will try get this backported to 18.06. So in theory the snapshot packages should also run on 18.06, but i did not specifically test this.
PS: I'm also currently working on a easy to use docker based package-builder, which should make it very easy for everyone to build/rebuild specific packages for 18.06/snapshot. So you can get the latest changes via custom feeds or use custom build options, without having to dig deep into the openwrt sdk framework.
You can also give this online image builder a shot: