move the man pages to the docs/ dir

Docker-DCO-1.1-Signed-off-by: SvenDowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
cp's -T and --reflink=auto are only available on GNU coreutils

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)
Benchmarks for engine/env

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Update libcontainer to 5210a236b92a8022a673108f347
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Update libcontainer references
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Rename libcontainer.Container to libcontainer.Config
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Merge pull request #6595 from LK4D4/env_benchmarks

Benchmarks for engine/env
Merge pull request #6650 from crosbymichael/update-libcontainer-post-refactor

Update libcontainer dep to 5210a236b92a8022a673108f347
Fix search integration-cli test

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #6643 from kzys/freebsd-cp

cp's -T and --reflink=auto are only available on GNU coreutils
Merge pull request #6629 from SvenDowideit/move-man-pages-to-docs

move the man pages to the docs/ dir
Merge pull request #6654 from vieux/fix_test_search

Fix search integration-cli test