[boost] [config] <iosfwd> and g++ 2.95

select_stdlib_config.hpp has just been changed to include <iosfwd> instead of <utility>. But g++ 2.95's standard library has its own iostreams implementation which doesn't define __STL_CONFIG_H. It does define __IOSFWD__, so maybe that could be checked for as well? Is it okay to commit the attached patch? I've changed sgi.hpp to go back to including <utility> if __STL_CONFIG_H isn't defined so that anything that checks for _STL_CONFIG_H will still work. Also, if __IOSFWD__ happens to be used in another library, it will fail to compile. Daniel