Encrypt to self for sent messages

[github-k8n]

When using OpenPGP encryption with carbon messages, the sent text can not be decrypted on other devices as it is only encrypted to the recipient, not to the sender's key.

Please add an option (or do it by default) to add your own key as recipients when encrypting the message.

See also https://github.com/siacs/Conversations/issues/558

[github-k8n]

Some quick and dirty patch that encrypts to the sender if the key was selected (works for me..)

--- pidgin-gpg.c    2011-01-12 21:03:30.000000000 +0100
+++ pidgin-gpg.c    2014-11-09 21:19:57.102561976 +0100
@@ -463,14 +463,16 @@
    gpgme_error_t error;
    gpgme_ctx_t ctx;
    gpgme_key_t key;
+   gpgme_key_t sender_key;
    gpgme_data_t plain,cipher;
    char* cipher_str = NULL;
    char* cipher_str_dup = NULL;
    size_t len;
-   gpgme_key_t key_arr[2];
+   gpgme_key_t key_arr[3];

    key_arr[0] = NULL;
    key_arr[1] = NULL;
+   key_arr[2] = NULL;

    // connect to gpgme
    gpgme_check_version (NULL);
@@ -491,6 +493,33 @@
    }
    key_arr[0] = key;

+   // check if user selected a main key
+   const char* sender_fpr = purple_prefs_get_string(PREF_MY_KEY);
+   if (sender_fpr == NULL)
+       sender_fpr = "";
+   if (strcmp(sender_fpr,"") != 0)
+   {
+       // connect to gpgme
+       gpgme_check_version (NULL);
+       error = gpgme_new(&ctx);
+       if (error)
+       {
+           purple_debug_error(PLUGIN_ID,"gpgme_new failed: %s %s\n",gpgme_strsource (error), gpgme_strerror (error));
+           return NULL;
+       }
+
+       // get key by fingerprint
+       error = gpgme_get_key(ctx,sender_fpr,&sender_key,0);
+       if (error || !sender_key)
+       {
+           purple_debug_error(PLUGIN_ID,"gpgme_get_key failed: %s %s\n",gpgme_strsource (error), gpgme_strerror (error));
+           gpgme_release (ctx);
+           return NULL;
+       }
+       key_arr[1] = sender_key;
+   }
+
+
    // create data containers
    gpgme_data_new_from_mem (&plain, plain_str,strlen(plain_str),1);
    gpgme_data_new(&cipher);

[github-k8n]

Created pull request with this and a few additional things for carbon copy support.
#14