Fix FindBoost.cmake to find Boost 1.64.0 beta

Minimal update to the module to enable finding components of Boost beta from the upcoming release.

---

Boost 1.64.0 beta has been published for testing. The Boost 1.64.0 beta snapshot recognises VS2017 toolset as msvc-14.10 with library name tag generated as vc1410 (see https://github.com/boostorg/config/pull/126).

Unfortunately, there is lots of confusion regarding versions uses in VS2017 and the toolset name used by Boost has not been fixed yet. Details in thread 1.64.0 Delayed because of Microsoft (version numbers). However, this small fix allows early testers to pass some initial hurdle.

This is a minimal/preliminary patch, it does not include update to inter-dependencies between Boost libraries.

I have successfully tested it using CMake 3.8.20170316-g2b86 with a Boost client project which requires:

-- Boost version: 1.64.0
-- Found the following Boost libraries:
--   date_time
--   chrono
--   filesystem
--   iostreams
--   program_options
--   regex
--   system
--   thread
--   zlib