Resync the DCO text with upstream at http://developercertificate.org/

```
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
```

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Add authenticated TLS support for API

Docker-DCO-1.1-Signed-off-by: Johannes 'fish' Ziemke <github@freigeist.org> (github: discordianfish)
Add proper support for relative WORKDIR instructions

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Disable automatic killing of containers when docker stop fails

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: cpuguy83)
add softlayer installation instructions

Docker-DCO-1.1-Signed-off-by: Andrea Turli <andrea.turli@gmail.com> (github: andreaturli)
address comments from @jamtur01

Docker-DCO-1.1-Signed-off-by: Andrea Turli <andrea.turli@gmail.com> (github: andreaturli)
add time since exit in docker ps

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Improve WORKDIR test to cover more edge cases

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Add some documentation about relative WORKDIR values

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Only unshare the mount namespace for execin

Fixes #4728
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
graphdriver: build tags

Enable build tags for all the graphdrivers to be excludable.

As an example:
```
$ go build
$ ls -l docker
-rwxr-xr-x 1 vbatts vbatts 18400158 Mar 14 14:22 docker*
$ go build -tags "exclude_graphdriver_aufs exclude_graphdriver_vfs exclude_graphdriver_devicemapper"
$ ls -l docker
-rwxr-xr-x 1 vbatts vbatts 17467068 Mar 14 14:22 docker*
```

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
runtime: no build tags for vfs driver

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Merge pull request #4731 from crosbymichael/fix-execin

Only unshare the mount namespace for execin
add env hint

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
devmapper: Increase timeout in waitClose to 10sec

As reported in https://github.com/dotcloud/docker/issues/4389 we're
currently seeing timeouts in waitClose on some systems. We already
bumped the timeout in waitRemove() in
https://github.com/dotcloud/docker/issues/4504.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Update ubuntulinux.rst

Adding the Docker repository key fails if port 11371 not open. This would probably work for more people.
Merge pull request #4738 from SvenDowideit/mention-env-scrubbing

add env hint
Merge pull request #4739 from alexlarsson/dm-timeout

devmapper: Increase timeout in waitClose to 10sec
Merge pull request #4674 from vbatts/vbatts-graphdriver_build_tags

graphdriver: build tags
Prevent dynamic allocation of previously allocated ports

Docker-DCO-1.1-Signed-off-by: Andy Kipp <andy@rstudio.com> (github: kippandrew)