* include/bits/ios_base.h (ios_base::io_state, ios_base::open_mode)
	(ios_base::seek_dir): Remove for C++17.
	* include/std/streambuf (basic_streambuf::stossc): Remove for C++17.
	Add deprecated attribute for C++11 and C++14.
	* testsuite/27_io/types/1.cc: Don't run for C++17 and later.
	* testsuite/27_io/types/4.cc: New.

From-SVN: r250531