Define a new exception type derived from std::ios::failure[abi:cxx11]
which also aggregates an object of the gcc4-compatible ios::failure
type. Make __throw_ios_failure throw this new type for iostream errors
that raise exceptions. Provide custom type info for the new type so that
it can be caught by handlers for the gcc4-compatible ios::failure type
as well as handlers for ios::failure[abi:cxx11] and its bases.

	PR libstdc++/85222
	* src/c++11/Makefile.am [ENABLE_DUAL_ABI]: Add special rules for
	cxx11-ios_failure.cc to rewrite type info for __ios_failure.
	* src/c++11/Makefile.in: Regenerate.
	* src/c++11/cxx11-ios_failure.cc (__ios_failure, __iosfail_type_info):
	New types.
	[_GLIBCXX_USE_DUAL_ABI] (__throw_ios_failure): Define here.
	* src/c++11/ios.cc (__throw_ios_failure): Remove definition.
	* src/c++98/ios_failure.cc (__construct_ios_failure)
	(__destroy_ios_failure, is_ios_failure_handler): New functions.
	[!_GLIBCXX_USE_DUAL_ABI] (__throw_ios_failure): Define here.
	* testsuite/27_io/ios_base/failure/dual_abi.cc: New.
	* testsuite/27_io/basic_ios/copyfmt/char/1.cc: Revert changes to
	handler types, to always catch std::ios_base::failure.
	* testsuite/27_io/basic_ios/exceptions/char/1.cc: Likewise.
	* testsuite/27_io/basic_istream/extractors_arithmetic/char/
	exceptions_failbit.cc: Likewise.
	* testsuite/27_io/basic_istream/extractors_arithmetic/wchar_t/
	exceptions_failbit.cc: Likewise.
	* testsuite/27_io/basic_istream/extractors_other/char/
	exceptions_null.cc: Likewise.
	* testsuite/27_io/basic_istream/extractors_other/wchar_t/
	exceptions_null.cc: Likewise.
	* testsuite/27_io/basic_istream/sentry/char/12297.cc: Likewise.
	* testsuite/27_io/basic_istream/sentry/wchar_t/12297.cc: Likewise.
	* testsuite/27_io/basic_ostream/inserters_other/char/
	exceptions_null.cc: Likewise.
	* testsuite/27_io/basic_ostream/inserters_other/wchar_t/
	exceptions_null.cc: Likewise.
	* testsuite/27_io/ios_base/storage/2.cc: Likewise.

From-SVN: r259281