Restore (merge-clobbered?) detach, join, interrupt method decls.

include/boost/fiber/fiber.hpp

@@ -116,6 +116,12 @@ public:
         return impl_ ? impl_->get_id() : id();
     }
 
+    void detach() noexcept;
+
+    void join();
+
+    void interrupt() noexcept;
+
     template <class PROPS>
     PROPS& properties()
     {