libstdc++: Fix std::exception_ptr regressions [PR103630]

libstdc++: Fix std::exception_ptr regressions [PR103630]

This restores support for std::make_exception_ptr<E&> and for using
std::exception_ptr in C++98.

Because the new non-throwing implementation needs to use std::decay to
handle references the original throwing implementation is used for
C++98.

We also need to change the typeid expression so it doesn't yield the
dynamic type when the function parameter is a reference to a polymorphic
type. Otherwise the new exception object could be caught by any handler
matching the dynamic type, even though the actual exception object is
only a copy of the base class, sliced to the static type.

libstdc++-v3/ChangeLog:

	PR libstdc++/103630
	* libsupc++/exception_ptr.h (exception_ptr): Fix exception
	specifications on inline definitions.
	(make_exception_ptr): Decay the template parameter. Use typeid
	of the static type.
	* testsuite/18_support/exception_ptr/103630.cc: New test.