Addd new constructors to containers, according to C++14's new constructors taking allocator arguments.

doc/container.qbk

@@ -1086,6 +1086,8 @@ use [*Boost.Container]? There are several reasons for that:
    and [*Boost.Intrusive]. Preprocessed code size have decreased considerably and compilation times have improved.
 *  Added `nth` and `index_of` functions to containers with random-access iterators (except `basic_string`).
 *  Added C++17's `allocator_traits<Allocator>::is_always_equal`.
+*  Updated containers to implement new constructors from C++14 (`Sequence(size_type, const allocator_type &)`, and related
+   constructors in set/map).
 *  Fixed bugs:
    * [@https://svn.boost.org/trac/boost/ticket/10790 Trac #10790 (['long long errors from container"])].
    * [@https://svn.boost.org/trac/boost/ticket/10808 Trac #10808 (['compare equal operator of vector is broken"])].