Including the transaction text into the purpose text

Some banks include additional purpose information for a transaction in
non-swift-section 17 (aka transaction text). If available, this
transaction text is put in front of the other purpose texts to provide
full transaction information.

While the final solution is still under discussion. This change is a
first low-impact implementation backported and distilled from the work
discussed in #139.

src/import-export/aqb/gnc-ab-utils.c

@@ -364,10 +364,18 @@ gchar *
 gnc_ab_get_purpose(const AB_TRANSACTION *ab_trans)
 {
     const GWEN_STRINGLIST *ab_purpose;
+    const char *ab_transactionText = NULL;
     gchar *gnc_description = NULL;
 
     g_return_val_if_fail(ab_trans, g_strdup(""));
 
+    /* According to AqBanking, some of the non-swift lines have a special
+     * meaning. Some banks place valuable text into the transaction text,
+     * hence we put this text in front of the purpose. */
+    ab_transactionText = AB_Transaction_GetTransactionText(ab_trans);
+    if (ab_transactionText)
+        gnc_description = g_strdup(ab_transactionText);
+
     ab_purpose = AB_Transaction_GetPurpose(ab_trans);
     if (ab_purpose)
         GWEN_StringList_ForEach(ab_purpose, join_ab_strings_cb,