Update to the latest stable versions of Boost, Folly and Wangle

[tdauth]

Since September 2017, the executors of Wangle have been moved to Folly, so there is no need for Wangle anymore: https://github.com/facebook/folly/commits/ac6b1e283b5f09a39f17a2c8014275135c808bfb/folly/executors/ThreadPoolExecutor.h

• Drop the dependency to Wangle and update to the latest versions of Boost and Folly.
• The latest version of Folly supports a CMake build rather than an automake build: https://github.com/facebook/folly/blob/master/README.md Still trying to figure out if it actually works on Fedora: https://github.com/facebook/folly/issues/923

Since Folly can be used as CMake package now and it is supported by CMake Hunter (https://github.com/ruslo/hunter/issues/838) maybe change to hunter to simplify the whole build process. Of course, we cannot use the latest releases/git versions of the repository then.

[tdauth]

Only Boost.Thread is missing now.

[tdauth]

We depend on Boost.Thread from the system now (find_package(Boost)) and only download and build Folly as CMake project.