[RELEASE] Released version 1.5.9

Released version 1.5.9 with the following main changes :
    - BUILD: fix "make install" to support spaces in the install dirs
    - BUG/MEDIUM: checks: fix conflicts between agent checks and ssl healthchecks
    - BUG/MEDIUM: ssl: fix bad ssl context init can cause segfault in case of OOM.
    - BUG/MINOR: samples: fix unnecessary memcopy converting binary to string.
    - BUG/MEDIUM: connection: sanitize PPv2 header length before parsing address information
    - BUG/MEDIUM: pattern: don't load more than once a pattern list.
    - BUG/MEDIUM: ssl: force a full GC in case of memory shortage
    - BUG/MINOR: config: don't inherit the default balance algorithm in frontends
    - BUG/MAJOR: frontend: initialize capture pointers earlier
    - BUG/MINOR: stats: correctly set the request/response analysers
    - DOC: fix typo in the body parser documentation for msg.sov
    - BUG/MINOR: peers: the buffer size is global.tune.bufsize, not trash.size
    - MINOR: sample: add a few basic internal fetches (nbproc, proc, stopping)
    - BUG/MAJOR: sessions: unlink session from list on out of memory
BUG/MEDIUM: patterns: previous fix was incomplete

Dmitry Sivachenko <trtrmitya@gmail.com> reported that commit 315ec42
("BUG/MEDIUM: pattern: don't load more than once a pattern list.")
relies on an uninitialised variable in the stack. While it used to
work fine during the tests, if the uninitialized variable is non-null,
some patterns may be aggregated if loaded multiple times, resulting in
slower processing, which was the original issue it tried to address.

The fix needs to be backported to 1.5.
(cherry picked from commit 4deaf39243c4d941998b1b0175bad05b8a287c0b)
BUG/MEDIUM: payload: ensure that a request channel is available

Denys Fedoryshchenko reported a segfault when using certain
sample fetch functions in the "tcp-request connection" rulesets
despite the warnings. This is because some tests for the existence
of the channel were missing.

The fetches which were fixed are :
  - req.ssl_hello_type
  - rep.ssl_hello_type
  - req.ssl_sni

This fix must be backported to 1.5.
(cherry picked from commit 83f2592bcd2e186beeabcba16be16faaab82bd39)