key-func.c (guile_ssh_private_key_from_file): Remove `session' parameter

* ssh/key-func.c (guile_ssh_private_key_from_file): Remove `session'
  parameter.  All callers updated.
* doc/api-keys.texi (Keys): Update description of
  `private-key-from-file'.
* examples/echo/client.scm.in (get-prvkey): Update.
* tests/key.scm ("private-key-from-file"): Update.
* tests/client-server.scm ("userauth-public-key!, success"): Update.
* NEWS: Update.
ssh/message-func.c: Fix warnings

* ssh/message-func.c (get_auth_req, get_pty_req, get_env_req)
  (get_exec_req, get_global_req, get_service_req, get_channel_open_req):
  Fix warnings: Add `const' qualifier where it is needed.
ssh/message-func.c (get_auth_req): Fix a bug

* ssh/message-func.c (get_auth_req): Fix a bug with assignment of
  `ssh_public_key' type to `ssh_key' variable: Use
  `ssh_message_auth_pubkey' instead of `ssh_message_auth_publickey' to
  get the key.
Merge branch 'master' into port-forwarding