implement {header,HeaderSize} option
change default active mode from false to true

The default active mode for gen_tcp is true, not false. Change it to be the
same for gen_utp.
update to latest version of libutp
add connect/4

In gen_tcp, connect/4 takes a timeout as the 4th parameter. Here, libutp
doesn't give us control over connect timeouts, so for now connect/4 just
ignores the timeout parameter and calls connect/3.