Document "since" of FB_DISCONNECT_TRANSACTION

Author: mrotteveel

jaybird-native/src/main/java/org/firebirdsql/gds/ng/jna/FbClientFeature.java

@@ -21,6 +21,9 @@ public enum FbClientFeature {
     STATEMENT_TIMEOUT("fb_dsql_set_timeout"),
     // Can be used to identify Firebird 3.0 or higher fbclient
     FB_PING("fb_ping"),
+    /**
+     * @since 6
+     */
     FB_DISCONNECT_TRANSACTION("fb_disconnect_transaction");
 
     // If a feature depends on multiple methods, consider changing this to a list or set