Without pcm, firefox will crash with this error when playing sound
```
parts/firefox/firefox: relocation error:
/srv/slapgrid/slappart11/srv/runner/software/88ef27d24c6e0a792f72f568146a3838/parts/firefox/libxul.so:
symbol snd_pcm_open, version ALSA_0.9 not defined in file libasound.so.2 with link time reference
```
libasound.so does not contain this symbol if built with --disable-pcm

that is a long-deprecated syntax and removed in haproxy 1.6.

version up : OpenSSL 1.0.2e, including CVE-2015-3193, CVE-2015-3194, CVE-2015-3195 and CVE-2015-3196.

https://www.openssl.org/news/secadv/20151203.txt

From https://golang.org/doc/devel/release.html#go1.5.minor:

    go1.5.2 (released 2015/12/02) includes bug fixes to the compiler,
    linker, and the mime/multipart, net, and runtime packages

/reviewed-by: TrustMe

If one wants to check URLs on UNIX-sockets, there is no full URL schema
in curl for this, but the following has to be used instead:

    curl --unix-socket /path/to/socket http:/<url-path>

For this to work, one can do e.g. the following trick:

    [promise-unicorn]
    recipe  = slapos.cookbook:check_url_available
    url     = --unix-socket ${unicorn:socket}  http:/

but then generated promise scripts fails this way:

    ./etc/promise/unicorn: line 7: [: too many arguments

via quoting $URL in emptiness check we can support both usual URLs and
urls with --unix-socket prepended trick.

/reviewed-by @cedric.leninivin  (on nexedi/slapos!31)

In gitlab SR a service I need to check - gitlab-workhorse, returns 200
only when request comes to some repository and authentication backend
allows it.

Requiring access to repositories is not very good just to check if the
service is alive, and also auth backend can be not alive, and initially
there are no repositories at all. So gitlab-workhorse is checked to be
alive by pinging it with non-existing URL and expecting 403.

For this to work we need to allow clients to specify expected HTTP code
instead of previously hardcoded 200 (which still remains the default).

/reviewed-by @cedric.leninivin  (on nexedi/slapos!31)

  The final file were not a valid json sometimes as some entries '0.0.0.0' or '::' were been ignored
  and an additionalcomman was added on the wrong place.

Both SPDY an gzip_static are needed for upcoming GitLab SR:

  - GitLab uses SPDY in its https nginx configuration, and
  - prepares compiled assets in pre-gzipped form on filesystem

both modules are off by default and need to be explicitly enabled with
corresponding directives, so this should not affect already used nginx
configurations.

/cc @kazuhiko, @jerome, @gabriel
/reviewed-by @rafael  (on nexedi/slapos!30)