[boost] [threads] making parts of Boost.Threads header-only

Hi, Looks like a sensible part of Boost.Threads, namely that dealing with mutexes and locks, would be header-only but for its relying on boost/thread/exceptions.hpp, whose implementation is located at /libs/thread/*/exceptions.cpp. Given that this .cpp mostly consists of extremely simple definitions (as simple as do-nothing functions in many cases), would it make sense to move this to inline definitions in boost/thread/exceptions.hpp thus making mutexes and locks header-only? This would greatly enhance the appeal of this part of Boost.Threads, as having to link a separate module is a considerable burden. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo