Retransmit last packet on timeout

Retransmit last packet on retransmit_timeout
Per connection recurring timer for retransmit or inactive check
more detailed debug

debug for retransmit attempt and packet sequence
unit tests

$connection->error after finish contains the error received
unit tests retransmit

same tests as 02-basic.t with retransmit enabled
win32 compatibility

do not use MSG_DONTWAIT on platforms that do not support it
bugfix: error

reverted buggy code
bugfix ack 0
retransmit tests
Merge pull request #6 from harry-bix/retransmit

Retransmit last packet on timeout