Log Message:
Changes 1.40.0:
* Build System improvements.
* Updated Libraries: Accumulators, Asio, Circular Buffer, Foreach, Function,
  Fusion, Hash, Interprocess, Intrusive, MPL, Program.Options, Proto, Random,
  Serialization, Unordered, Xpressive.

Changes 1.39.0:
* New Libraries: Signals2.
* Updated Libraries: Asio, Flyweight, Foreach, Hash, Interprocess, Intrusive,
  Program.Options, Proto, PtrContainer, Range, Unordered, Xpressive.
* Updated Tools: Boostbook, Quickbook.