François Dumont  <fdumont@gcc.gnu.org>

	* include/bits/streambuf_iterator.h
	(istreambuf_iterator<>::operator*()): Do not capture iterator state
	in Debug assertion.
	(istreambuf_iterator<>::operator++()): Likewise and remove _M_sbuf check.
	(istreambuf_iterator<>::operator++(int)): Likewise.
	(istreambuf_iterator<>::_M_get()): Remove _M_c assignment.
	(istreambuf_iterator<>::_S_is_eof()): New.
	(istreambuf_iterator<>::_M_at_eof()): Adapt, use latter.
	(find(istreambuf_iterator<>, istreambuf_iterator<>, _CharT)):
	Return an iterator with _M_c set to eof to capture streambuf state
	on evaluation.
	(testsuite/24_iterators/istreambuf_iterator/2.cc): Add checks.

Co-Authored-By: François Dumont <fdumont@gcc.gnu.org>

From-SVN: r253417