DOC: add some information on capture.(req|res).hdr

Clarify the beginning of the index.
MINOR: http: capture.req.method and capture.req.uri

Add 2 sample fetchs allowing to extract the method and the uri of an
HTTP request.

FIXME: the sample fetches parser can't add the LW_REQ requirement, at
the moment this flag is used automatically when you use sample fetches.

Note: also fixed the alphabetical order of other capture.req.* keywords
in the doc.
BUG/MINOR: tcpcheck connect wrong behavior

A typo made first step of a tcpcheck to be a connect step. This patch
prevents this behavior. The bug was introduced in 1.5-dev22 with
"tcp-check connect" and only affects these directives. No backport is
needed.
MINOR: session: clean up the connection free code

Use conn_free() instead of pool_free2(conn...). This makes the code more
auditable.
MINOR: http: optimize capture.req.method and capture.req.uri

Useless strncpy were done in those two sample fetches, the
"struct chunk" allows us to dump the specified len.

The encode_string() in capture.req.uri was judged inappropriate and was
deleted.

The return type was fixed to SMP_T_CSTR.
BUG/MEDIUM: checks: immediately report a connection success

When no check type is configured (so the basic connection check), we
want the connection success to be immediately reported. Unfortunately,
it did not happen because in this case the connection is not registered
for read nor for write, and the wake_srv() callback does not handle this
case where no data transfer was requested. However, having option tcp-check
hides this problem because the check type follows a different setup mode,
by having check->type != 0 and the connection believing it must try to
send data.

The effect was that without any option, checks would succeed only at the
end of the check interval. So let's just add the wake-up condition.

This bug appeared with the recent polling changes, no backport is needed.
As a workaround, using "option tcp-check" fixes the problem.
Merge branch 'master' of http://git.1wt.eu/git/haproxy