ssh: allow adding ed25519 keys to the agent

Fixes golang/go#15701

Change-Id: I561701e38b9d434ef44448bdbcfab203f3c31d99
Reviewed-on: https://go-review.googlesource.com/23141
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2 files changed