Merge branch 'develop'

Merge branch 'develop'

Merge branch 'develop'

Merge pull request boostorg#4 from Lastique/patch-1

Use public interface of Boost.Iterator

Tested on Darwin with clang-5.1.

Merge pull request boostorg#2 from danieljames/cherry-pick

Cherry pick some old documentation changes.

Merge pull request boostorg#2 from danieljames/cherry-pick

Cherry pick some old documentation changes.

Release 1.55.0

[SVN r86621]

Release 1.54.0

[SVN r84923]

Release 1.54.0 beta1

[SVN r84619]

Release 1.53.0

[SVN r82734]