Limit operations on vector::pointer to NullablePointer requirements.

	* include/bits/stl_vector.h (_Vector_base::_Vector_impl,
	_Vector_base::_M_allocate): NullablePointer requirements do not
	include initialization from literal zero, use value-initialization.
	* include/bits/vector.tcc (vector::_M_insert_aux,
	vector::_M_explace_back_aux): Likewise for assignment.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@209377 138bc75d-0d04-0410-961f-82ee72b054a4
	* include/bits/allocator.h (operator==, operator!=): Add exception
	specifications.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@209379 138bc75d-0d04-0410-961f-82ee72b054a4
	PR libstdc++/60497
	* include/std/tuple (get): Qualify calls to prevent ADL.
	* testsuite/20_util/tuple/60497.cc: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@209381 138bc75d-0d04-0410-961f-82ee72b054a4