hashtable_policy.h (__details::_Before_begin<>): New, combine a base node instance...

hashtable_policy.h (__details::_Before_begin<>): New, combine a base node instance and an allocator.

2012-11-01  François Dumont  <fdumont@gcc.gnu.org>

	* include/bits/hashtable_policy.h (__details::_Before_begin<>):
	New, combine a base node instance and an allocator.
	* include/bits/hashtable.h (_Hashtable<>::_M_node_allocator): Remove.
	(_Hashtable<>::_M_before_begin): Rename into _M_bbegin and type
	modified to __detail::_Before_begin<>.
	(_Hashtable<>::_M_node_allocator()): New, get the node allocator
	part of _M_bbegin.
	(_Hashtable<>::_M_before_begin()): New, get the before begin node
	part of _M_bbegin.
	(_Hashtable<>): Adapt to use latter.

From-SVN: r193068