Support the not anymore patented IDEA cipher algorithm.

* cipher/idea.c: New.  Take from Libgcrypt master and adjust for
direct use in GnuPG.
* cipher/idea-stub.c: Remove.
* cipher/Makefile.am: Add idea.c and remove idea-stub.c rules.
* configure.ac: Remove idea-stub code.
* g10/gpg.c (check_permissions): Remove code path for ITEM==2.
(main): Make --load-extension a dummy option.
* g10/keygen.c (keygen_set_std_prefs): Include IDEA only in PGP2
compatibility mode.
* g10/misc.c (idea_cipher_warn): Remove.  Also remove all callers.
* g10/seckey-cert.c (do_check): Remove emitting of STATUS_RSA_OR_IDEA.
* g10/status.c (get_status_string): Remove STATUS_RSA_OR_IDEA.
* g10/status.h (STATUS_RSA_OR_IDEA): Remove.

--

To keep the number of actually used algorithms low, we support IDEA
only in a basically read-only way (unless --pgp2 is used during key
generation).  It does not make sense to suggest the use of this old 64
bit blocksize algorithm.  However, there is old data available where
it might be helpful to have IDEA available.

doc/DETAILS

@@ -115,7 +115,7 @@ record.
             available. The advantage of using this value is that it is
             guaranteed to have been been build by the same lookup
             algorithm as gpgsm uses.
-            For "uid" recods this lists the preferences n the sameway the 
+            For "uid" recods this lists the preferences n the sameway the
             -edit menu does.
 	    For "sig" records, this is the fingerprint of the key that
 	    issued the signature.  Note that this is only filled in if
@@ -280,8 +280,8 @@ more arguments in future versions.
 
     UNEXPECTED <what>
         Unexpected data has been encountered
-            0 - not further specified               1       
-  
+            0 - not further specified               1
+
 
     TRUST_UNDEFINED <error token>
     TRUST_NEVER  <error token>
@@ -296,7 +296,7 @@ more arguments in future versions.
     PKA_TRUST_BAD  <mailbox>
         Depending on the outcome of the PKA check one of the above
         status codes is emitted in addition to a TRUST_* status.
-        Without PKA info available or 
+        Without PKA info available or
 
     SIGEXPIRED
 	This is deprecated in favor of KEYEXPIRED.
@@ -316,11 +316,9 @@ more arguments in future versions.
 	The ASCII armor is corrupted.  No arguments yet.
 
     RSA_OR_IDEA
-	The IDEA algorithms has been used in the data.  A
-	program might want to fallback to another program to handle
-	the data if GnuPG failed.  This status message used to be emitted
-        also for RSA but this has been dropped after the RSA patent expired.
-        However we can't change the name of the message.
+	Obsolete.  This status message used to be emitted for requests
+        to use the IDEA or RSA algorithms.  It has been dropped from
+        GnuPG 1.4 after the respective patents expired.
 
     SHM_INFO
     SHM_GET
@@ -389,7 +387,7 @@ more arguments in future versions.
           1 := Entirely new key.
           2 := New user IDs
           4 := New signatures
-          8 := New subkeys 
+          8 := New subkeys
          16 := Contains private key.
         The flags may be ORed.
 
@@ -410,7 +408,7 @@ more arguments in future versions.
 	operation:
 	    1 - verify
             2 - encrypt
-            3 - decrypt        
+            3 - decrypt
 
     FILE_DONE
 	Marks the end of a file processing which has been started
@@ -457,7 +455,7 @@ more arguments in future versions.
              "starting_agent" - A gpg-agent was started because it is not
                           running as a daemon.
 
-        
+
     SIG_CREATED <type> <pubkey algo> <hash algo> <class> <timestamp> <key fpr>
 	A signature has been created using these parameters.
 	    type:  'D' = detached
@@ -469,7 +467,7 @@ more arguments in future versions.
         Note, that TIMESTAMP may either be a number with seconds since
         epoch or an ISO 8601 string which can be detected by the
         presence of the letter 'T' inside.
-        
+
     KEY_CREATED <type> <fingerprint> [<handle>]
         A key has been created
             type: 'B' = primary and subkey
@@ -490,13 +488,13 @@ more arguments in future versions.
 	is used.  The format is suitable to be passed to the option
 	--override-session-key
 
-    NOTATION_NAME <name> 
+    NOTATION_NAME <name>
     NOTATION_DATA <string>
         name and string are %XX escaped; the data may be splitted
         among several notation_data lines.
 
     USERID_HINT <long main keyid> <string>
-        Give a hint about the user ID for a certain keyID. 
+        Give a hint about the user ID for a certain keyID.
 
     POLICY_URL <string>
         string is %XX escaped
@@ -533,7 +531,7 @@ more arguments in future versions.
         The output was truncated to MAXNO items.  This status code is issued
         for certain external requests
 
-    ERROR <error location> <error code> 
+    ERROR <error location> <error code>
 
         This is a generic error status message, it might be followed
         by error location specific data. <error token> and
@@ -1144,12 +1142,12 @@ Here is the format we use for detached signatures:
 "@B"  - Detached signature follows.
         This emits a control packet (1,'B')
 <detached_signature>
-"@t"  - Signed text follows. 
+"@t"  - Signed text follows.
         This emits the control packet (2, 'B')
 <signed_text>
 "@."  - End of operation. The final control packet forces signature
         verification
-"@>"  - End of stream   
+"@>"  - End of stream