http2/h2i: disable building h2i on plan9 and solaris
http2/h2i: disable building h2i on plan9 and solaris

They lack terminal.MakeRaw and terminal.Restore.

Updates golang/go#11811

Change-Id: I1e5d8ca90b2f9c13fe7a6396c2f86e0a5b392b84
Reviewed-on: https://go-review.googlesource.com/18577
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Reviewed-by: Chris Broadfoot <0c2851a4f8ab4aa5606e69c0757771dd13dbe686@golang.org>

albertjin/golang-net,albertjin/golang-net,DramaFever/golang.org-x-net,cmars/tools,DramaFever/golang.org-x-net,cmars/tools,golang/net,cesanta/goxnet,cesanta/goxnet,cmars/tools,cmars/tools