2014-01-28  Jonathan Wakely  <jwakely@redhat.com>
	    Kyle Lippincott  <spectral@google.com>

	PR libstdc++/59656
	* include/bits/shared_ptr.h (shared_ptr): Add new non-throwing
	constructor and grant friendship to weak_ptr.
	(weak_ptr::lock()): Use new constructor.
	* include/bits/shared_ptr_base.h
	(_Sp_counted_base::_M_add_ref_lock_nothrow()): Declare new function
	and define specializations.
	(__shared_count): Add new non-throwing constructor.
	(__shared_ptr): Add new non-throwing constructor and grant friendship
	to __weak_ptr.
	(__weak_ptr::lock()): Use new constructor.
	* testsuite/20_util/shared_ptr/cons/43820_neg.cc: Adjust dg-error.
	* testsuite/20_util/shared_ptr/cons/void_neg.cc: Likewise.

Co-Authored-By: Kyle Lippincott <spectral@google.com>

From-SVN: r207180