std_bitset.h (_Base_bitset::_M_do_left_shift, [...]): Expect a non-zero shift.

2002-12-26  Phil Edwards  <pme@gcc.gnu.org>

	* include/std/std_bitset.h (_Base_bitset::_M_do_left_shift,
	_Base_bitset::_M_do_right_shift): Expect a non-zero shift.
	(bitset::operator<<=, bitset::operator>>=):  When shifting more bits
	than are in the bitset, zero memory rather than segfault.
	(operator>>(basic_istream,bitset):  Only call setstate once, after
	all work has been done.

	* testsuite/23_containers/bitset_members.cc (test03):  New test.
	* testsuite/23_containers/bitset_shift.cc (test02):  New test.

From-SVN: r60533