[U-Boot] [ANN] U-Boot v2015.04-rc4 released

Hey all,

I've pushed v2015.04-rc4 out to the repository and tarballs should exist soon.

We're getting really close to the end and I hope we'll have a few more small PRs come along with this and that. I think we're looking to be in decent shape overall but there's a few platforms that keep not building without errors / warnings (katmai, openrd*) and I wonder if we shouldn't just drop them.

As always, if anything else is broken please speak up.

Thanks all!