tempfork: temporarily fork gliderlabs/ssh and x/crypto/ssh

While we rearrange/upstream things.

gliderlabs/ssh is forked into tempfork from our prior fork
at be8b7add40

x/crypto/ssh OTOH is forked at
https://github.com/tailscale/golang-x-crypto because it was gnarlier
to vendor with various internal packages, etc.
Its git history shows where it starts (2c7772ba30643b7a2026cbea938420dce7c6384d).

Updates #3802

Change-Id: I546e5cdf831cfc030a6c42557c0ad2c58766c65f
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

tempfork/gliderlabs/ssh/ssh_test.go

@@ -0,0 +1,17 @@
+package ssh
+
+import (
+	"testing"
+)
+
+func TestKeysEqual(t *testing.T) {
+	defer func() {
+		if r := recover(); r != nil {
+			t.Errorf("The code did panic")
+		}
+	}()
+
+	if KeysEqual(nil, nil) {
+		t.Error("two nil keys should not return true")
+	}
+}