Thread: fix bug on future::then when the continuation is void() ir T&().

svn path=/trunk/boost/thread/; revision=84685
Thread: update future doc with void set_exception_at_thread_exit(E p).

svn path=/trunk/libs/thread/; revision=84688
Thread: cleanup test_8596.cpp.

svn path=/trunk/libs/thread/; revision=84689
Thread: update doc external_locking.qbk to remove const in mutex() function.

svn path=/trunk/libs/thread/; revision=84690
Thread: Added  test_8674.cpp test.

svn path=/trunk/libs/thread/; revision=84691
Thread: force use of chrono on windows.

svn path=/trunk/boost/thread/; revision=84709
Thread: take in account wait_abandoned.

svn path=/trunk/boost/thread/; revision=84710
Thread: update history and document force use of Boost.Chrono on windows platforms.

svn path=/trunk/libs/thread/; revision=84711
Thread: remove const on strict locks mutex() function.

svn path=/trunk/boost/thread/; revision=84712
Thread: used cons& in deleted constructors and assignment simulation.

svn path=/trunk/boost/thread/; revision=84718
Thread: Added future::unwrap()/get_or()/fallback_to().

svn path=/trunk/libs/thread/; revision=84719