Docs: add ApiVersion to /version for remote API 1.12

Docker-DCO-1.1-Signed-off-by: Paul Morie <pmorie@gmail.com> (github: pmorie)
Don't exit on eof in header reading in stdcopy

There was random lines drops in docker logs because of this
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Linking containers added to API example

Linking containers was not covered in the API documentation. I looked it up in the client source code and testing it manually.
Adds info on how to get env vars from container

Currently the docs just say "let's go into the container and look at the
env vars", but doesn't show how to do it.  It is also not currently
possible to enter the container as it is written in the doc
( container started with app.py and then somehow later on we have a
shell in the same container )

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: cpuguy83)
Increase time before exit in TestMultipleAttachRestart

Sometimes third attacher attaching to already stopped container.
Also I've changed prefix to attach and fixed cleanup on Fatal.
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
docs: add spotify docker-client link

Docker-DCO-1.1-Signed-off-by: Daniel Norberg <daniel.norberg@gmail.com> (github: danielnorberg)
Add helper function to make prctl system call.
Docker-DCO-1.1-Signed-off-by: Mrunal Patel <mrunalp@gmail.com> (github: mrunalp)
Merge pull request #6416 from danielnorberg/dano/docs-spotify-client

docs: add spotify docker-client link
Note user name and password in docs on boot2docker

Docker-DCO-1.1-Signed-off-by: Nathan LeClaire <nathan.leclaire@docker.com> (github: nathanleclaire)
Merge pull request #6421 from nathanleclaire/doc_fix

Note user name and password in docs on boot2docker
Fixed whitespace errors
Merge pull request #6386 from cpuguy83/fix_link_docs

Adds info on how to get env vars from container
Fix several man page spelling errors

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Fix missing leading slash for /bin/bash executable
Merge pull request #6429 from mika/patch-1

Fix missing leading slash for /bin/bash executable
Do inspect under container lock

It fixes some race conditions
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Fix several typos

Docker-DCO-1.1-Signed-off-by: Michael Prokop <github@michael-prokop.at> (github: mika)
Merge pull request #6431 from mika/mika/typos

Fix several typos
Fix spelling and grammar errors; remove seemingly out-of-place words

Docker-DCO-1.1-Signed-off-by: AJ Bowen <aj@gandi.net> (github: soulshake)
Fixed headers and ' characters

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)