crypto: add import comments.

Change-Id: I33240faf1b8620d0cd600de661928d8e422ebdbc
Reviewed-on: https://go-review.googlesource.com/1235
Reviewed-by: Andrew Gerrand <adg@golang.org>

ssh/doc.go

@@ -15,4 +15,4 @@ References:
   [PROTOCOL.certkeys]: http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/PROTOCOL.certkeys
   [SSH-PARAMETERS]:    http://www.iana.org/assignments/ssh-parameters/ssh-parameters.xml#ssh-parameters-1
 */
-package ssh
+package ssh // import "golang.org/x/crypto/ssh"