re PR libstdc++/56193 (ios_base should replace operator void* with explicit operator bool in C++11 onwards.)

	PR libstdc++/56193
	* config/abi/pre/gnu.ver: Add new exports.
	* include/bits/basic_ios.h (basic_ios::operator bool): Define.
	* src/c++98/ios_locale.cc (basic_ios::operator void*): Instantiate.

From-SVN: r215571