Address compilation warnings due to 2016-01-03 mml refactoring.

* lisp/gnus/mml-sec.el (password-cache, mm-encode): Require.
(message-options-get): Autoload.
(message-options-set): Declare.
(mml-secure-cache-passphrase, mml-secure-passphrase-cache-expiry):
Simplify default value.
* lisp/gnus/mml-smime.el (message-options-set): Remove declaration.
* lisp/gnus/mml1991.el, lisp/gnus/mml2015.el:
No longer a need for password-cache.

lisp/gnus/mml-sec.el

@@ -27,6 +27,8 @@
 
 (require 'gnus-util)
 (require 'epg)
+(require 'password-cache)
+(require 'mm-encode)
 
 (autoload 'mail-strip-quoted-names "mail-utils")
 (autoload 'mml2015-sign "mml2015")
@@ -35,6 +37,7 @@
 (autoload 'mml1991-encrypt "mml1991")
 (autoload 'message-fetch-field "message")
 (autoload 'message-goto-body "message")
+(autoload 'message-options-get "message")
 (autoload 'mml-insert-tag "mml")
 (autoload 'mml-smime-sign "mml-smime")
 (autoload 'mml-smime-encrypt "mml-smime")
@@ -44,6 +47,8 @@
 (autoload 'mml-smime-verify-test "mml-smime")
 (autoload 'epa--select-keys "epa")
 
+(declare-function message-options-set "message" (symbol value))
+
 (defvar mml-sign-alist
   '(("smime"     mml-smime-sign-buffer     mml-smime-sign-query)
     ("pgp"       mml-pgp-sign-buffer       list)
@@ -110,20 +115,15 @@ details."
   :group 'message
   :type 'boolean)
 
-(defcustom mml-secure-cache-passphrase
-  (if (boundp 'password-cache)
-      password-cache
-    t)
+;; FIXME If it's "NOT recommended", why is it the default?
+(defcustom mml-secure-cache-passphrase password-cache
   "If t, cache OpenPGP or S/MIME passphrases inside Emacs.
 Passphrase caching in Emacs is NOT recommended.  Use gpg-agent instead.
 See Info node `(message) Security'."
   :group 'message
   :type 'boolean)
 
-(defcustom mml-secure-passphrase-cache-expiry
-  (if (boundp 'password-cache-expiry)
-      password-cache-expiry
-    16)
+(defcustom mml-secure-passphrase-cache-expiry password-cache-expiry
   "How many seconds the passphrase is cached.
 Whether the passphrase is cached at all is controlled by
 `mml-secure-cache-passphrase'."

lisp/gnus/mml-smime.el

@@ -356,10 +356,6 @@ Whether the passphrase is cached at all is controlled by
 
 (autoload 'mml-compute-boundary "mml")
 
-;; We require mm-decode, which requires mm-bodies, which autoloads
-;; message-options-get (!).
-(declare-function message-options-set "message" (symbol value))
-
 (defun mml-smime-epg-sign (cont)
   (let ((inhibit-redisplay t)
 	(boundary (mml-compute-boundary cont)))

lisp/gnus/mml1991.el

@@ -25,11 +25,6 @@
 
 ;;; Code:
 
-(eval-and-compile
-  (if (locate-library "password-cache")
-      (require 'password-cache)
-    (require 'password)))
-
 (eval-when-compile
   (require 'cl)
   (require 'mm-util))

lisp/gnus/mml2015.el

@@ -27,11 +27,6 @@
 
 ;;; Code:
 
-(eval-and-compile
-  (if (locate-library "password-cache")
-      (require 'password-cache)
-    (require 'password)))
-
 (eval-when-compile (require 'cl))
 (require 'mm-decode)
 (require 'mm-util)