Make patty_ax25_sock_ack() return 1 if N(R) = V(A)

Make patty_ax25_sock_ack() return 1 if N(R) = V(A), to provide a
convenient means of verifying that an acknowledgement from the peer is
at least valid for current sequence variables, even if no new frames are
acknowledged; patty_ax25_sock_ack_pending() can always be used to
determine when frames are still pending acknowledgement

src/sock.c

@@ -791,6 +791,10 @@ int patty_ax25_sock_ack(patty_ax25_sock *sock, int nr) {
         max = nr,
         i;
 
+    if (min == max) {
+        return 1;
+    }
+
     if (max < min) {
         max += sock->mode == PATTY_AX25_SOCK_SABME? 128: 8;
     }