Avoid deprecation warning with -Wsystem-headers
C++17 says to use std::uncaught_exceptions() here instead of
std::uncaught_exception() but since we only care whether the result is
non-zero (and we aren't planning to remove the deprecated version) we
can just keep using std::uncaught_exception() and suppress the warning.
* include/std/ostream (basic_ostream::sentry::~sentry): Suppress
deprecation warnings for using uncaught_exception().
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@263593 138bc75d-0d04-0410-961f-82ee72b054a4