haproxy 1.3.12.3 - preview release

Hi guys,

I've just finished merging pending patches for 1.3.12.3. Those are generally minor changes but relevant ones, as reported by the short log :

---
Alexandre Cassen (1):


      [MINOR] add the "nolinger" option to disable data lingering


Krzysztof Oledzki (4):


      [BUG] fix double-free during clean exit

      [MINOR] prevent the system from sending an RST when closing health-checks

      [MEDIUM] do not add a cache-control: header when on non-cacheable responses

      [MEDIUM] Spread health checks even more


Willy Tarreau (3):


      [MEDIUM] only consider slow checks when looking for the common interval

      [MINOR] spread checks also when the server is OK.

      [DOC] document spread-checks

---

I have yet to check whether the reload problem reported by Jeremy is fixed
by Krzysztof's double-free fix. It's very very likely, since the scenario
to reproduce it matches the pattern required to trigger the double-free.

Among interesting changes are the "nolinger" patch from Alexandre which adds
an option to frontends and backends to disable data lingering. This generally
dramatically reduces the number of FIN_WAIT sockets in unreliable environments.

The other one is the spread checks from Krzysztof. It considerably reduced the
time needed to send the first check to servers, while ensuring that they when
a same server is present in multiple backends, it will not get all the checks
at once. The rest is good for 1.3.12 too.

I've put a pre-release here :

   http://haproxy.1wt.eu/download/1.3/test/haproxy-1.3.12.2-1.3.12.3-rc1.diff

If some of you want to ensure they don't see any regression before I release
it, it would be cool. I'll probably do that tomorrow or the day after, depending
on my spare time.

Thanks,
Willy