* tcp: bugfix for seq not in snd/rcv.wnd error * accept dupe ACKs for window updates and prevent decrement of UNA * add fixes for incorrect tcp functioning * remove Conn.Available* methods in favor of Conn.Free* methods due to ambiguous name
* tcp: add test replicating bugs and 32bit panic with GOARCH=386 * tcp: reject SYN on synchronized connections; fix maxSend underflow