clarify tcp linger option

[vans163]

This updates the documentation because the current is very confusing.

[CLAassistant]

All committers have signed the CLA.

[essen]

Right but now it's missing the info about the timeout being ignored when the first element is false.

[vans163]

right yea

[bmk]

Hi,

After some discussions, we have a proposal to make the three
'linger' alternatives more clear. See below:

/BMK

---

The first component is if linger is enabled, the second component
is the flushing time-out, in seconds. There are 3 alternatives:

1) {false, _}
   close/1 or shutdown/2 returns immediately, not waiting for data to
   be flushed, with closing happening in the background.
2) {true,  0}
   Aborts the connection when it is closed.
   Discards any data still remaining in the send buffers and sends RST
   to the peer.
   This avoids TCP's TIME_WAIT state, but leaves open the possibility
   that another "incarnation" of this connection being created.
3) {true,  Time} when Time > 0
   close/1 or shutdown/2 will not return until all queued messages for
   the socket have been successfully sent or the linger timeout (Time)
   has been reached.

[bmk]

HI,

I have now merged our proposal into master.

Regards,
/BMK