nixos/graphite-service: fix startup issue

The preStart snippets (graphite, carbon) try to create directories under
/var/db/. That currently fails because the code is run as user
"graphite". Fix by setting "PermissionsStartOnly = true" so that the
preStart stuff is run as 'root'.

Further:
 * graphite-web-0.9.12/bin/build-index.sh needs perl, so add it to PATH.
 * Now that preStart runs as root, we must wait with "chown graphite"
   until we're done creating files/directories.
 * Drop needless check for root (uid 0) before running chown.
nixos/grahite-service: mkdir -m => mkdir && chmod

mkdir -m will only set the permissions if it *creates* the directory.
Existing directories, with possibly wrong permissions, will not be
updated.

Use explicit chmod so permissions will always be correct.
herbstluftwm: update to 0.6.2
jdk7: update patchversion 51 -> 55.
Bump mpv to 0.3.8
Add subtitle option for ffmpeg.
Fix whitespace
libmx: Add package
eigen: upgrading version to 3.2.1
libgnurl, a fork of libcurl used by GNUnet
gnunet: add libgnurl and GnuTLS as dependencies

libgnurl is essential for bootstrapping (needed to download a hostlist).
GnuTLS is needed by gnunet-gns-proxy.

Also sort dependencies alphabetically.
Shea told me composableDerivation is hard to understand.

Thus comment it and why it was written long time ago until it'll get replaced piecewise.
Add licenses for CompCert/Z3

Both of these allow for binary redistribution.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
z3/verifast: update license

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixpkgs: add CompCert

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixpkgs: move frama-c to a more appropriate directory

Signed-off-by: Austin Seipp <aseipp@pobox.com>
btsync: Default to no login/password for the Web UI

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nginx: build http_stub_status module

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nixos: overhaul datadog module

This overhauls the Datadog module a bit to be much more useful. In
particular, it adds support for nginx and postgresql monitoring
integrations to dd-agent. These have to exist in separate files under
/etc/dd-agent, so the module just exposes then as separate options. In
the future, more integrations could be added this way.

In the process of doing this, I also had to rename the dd-agent user to
datadog. Note the UIDs did not change, so this is strictly backwards
compatible. The reason for this is to make it easier to create a
'datadog' postgres user with access to pg_stats, as 'dd-agent' typically
isn't a valid username. This allows the out of the box configurations to
be used.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
nginx: upgrade to 1.6.0, expose many more modules

By default, we now build all the optional nginx modules, including the
out-of-band ones like moreheaders and rtmp support.

Signed-off-by: Austin Seipp <aseipp@pobox.com>