[release] Boost 1.64.0

Release 1.64.0 of the Boost C++ Libraries is now available.

These open-source libraries work well with the C++ Standard Library, and
are usable across a broad spectrum of applications. The Boost license
encourages both commercial and non-commercial use.

This release contains one new library and numerous enhancements and bug
fixes for existing libraries.

For details, including download links, see <
http://www.boost.org/users/history/version_1_64_0.html>

You can also download directly from: <
https://dl.bintray.com/boostorg/release/1.64.0/>

To install this release on your system, see <
http://www.boost.org/doc/libs/release/more/getting_started/index.html>

Thanks to everyone who participated in this release.

Thanks,

-- The Boost Release Team

Vladimir Prus, Rene Rivera, Marshall Clow, Eric Niebler, Daniel James,
Beman Dawes