gpg: Allow only OCB for AEAD encryption.

* g10/gpg.c (opts): New option--force-ocb as alias for force-aead.
Turn --aead-algo and --personal-aead-preferences into dummy options.
(build_list_md_test_algo, build_list_aead_algo_name): Remove.
(my_strusage): Remove output of AEAD algos.
(main): Remove code from the --aead options.
* g10/encrypt.c (encrypt_seskey): Make file local.
(use_aead): Remove requirement for rfc4880bis.  Always return
AEAD_ALGO_OCB.
* g10/main.h (DEFAULT_AEAD_ALGO): Removed unused macro.
* g10/misc.c (default_aead_algo): Remove.
* g10/pkclist.c (select_aead_from_pklist): Return AEAD_ALGO_OCB or 0.
(select_algo_from_prefs): Remove personal AEAD algo setting.
* g10/keygen.c (keygen_set_std_prefs): Remove AEAD preference option
parsing.
* g10/options.h (opt): Remove def_aead_algo and personal_aead_prefs.
--

Due to the meanwhile expired patent on OCB there is no more reason for
using EAX.  Thus we forcefully use OCB if the AEAD feature flag is set
on a key.

doc/gpg.texi

@@ -2760,12 +2760,14 @@ is the default.
 @itemx --no-force-v4-certs
 These options are obsolete and have no effect since GnuPG 2.1.
 
-@item --force-aead
+@item --force-ocb
+@itemx --force-aead
+@opindex force-ocb
 @opindex force-aead
 Force the use of AEAD encryption over MDC encryption.  AEAD is a
 modern and faster way to do authenticated encryption than the old MDC
-method.  See also options @option{--aead-algo} and
-@option{--chunk-size}.
+method.  @option{--force-aead} is an alias and deprecated.  See also
+option @option{--chunk-size}.
 
 @item --force-mdc
 @itemx --disable-mdc
@@ -2810,16 +2812,6 @@ preferences, as GPG will only select an algorithm that is usable by
 all recipients.  The most highly ranked cipher in this list is also
 used for the @option{--symmetric} encryption command.
 
-@item --personal-aead-preferences @var{string}
-@opindex personal-aead-preferences
-Set the list of personal AEAD preferences to @var{string}.  Use
-@command{@gpgname --version} to get a list of available algorithms,
-and use @code{none} to set no preference at all.  This allows the user
-to safely override the algorithm chosen by the recipient key
-preferences, as GPG will only select an algorithm that is usable by
-all recipients.  The most highly ranked cipher in this list is also
-used for the @option{--symmetric} encryption command.
-
 @item --personal-digest-preferences @var{string}
 @opindex personal-digest-preferences
 Set the list of personal digest preferences to @var{string}.  Use
@@ -3233,16 +3225,6 @@ it allows you to violate the OpenPGP standard.  The option
 @option{--personal-cipher-preferences} is the safe way to accomplish the
 same thing.
 
-@item --aead-algo @var{name}
-@opindex aead-algo
-Specify that the AEAD algorithm @var{name} is to be used.  This is
-useful for symmetric encryption where no key preference are available
-to select the AEAD algorithm.  Running @command{@gpgname} with option
-@option{--version} shows the available AEAD algorithms.  In general,
-you do not want to use this option as it allows you to violate the
-OpenPGP standard.  The option @option{--personal-aead-preferences} is
-the safe way to accomplish the same thing.
-
 @item --digest-algo @var{name}
 @opindex digest-algo
 Use @var{name} as the message digest algorithm. Running the program
@@ -3786,6 +3768,13 @@ it. These options are deprecated. Use @option{--list-options
 [no-]show-policy-url} and/or @option{--verify-options
 [no-]show-policy-url} instead.
 
+@item --personal-aead-preferences @var{string}
+@opindex personal-aead-preferences
+This option is deprecated and has no more effect since version 2.3.9.
+
+@item --aead-algo @var{name}
+This option is deprecated and has no more effect since version 2.3.9.
+
 
 @end table