When an exceptional future is ignored, we print a message, and for an
std::exception we print its what(). However, it would be useful to also
see the exception's type. We already had such exception type printing
code for engine_exit(), and this patch extracts that code into a separate
function, and also uses it to print the warning message when an exceptional
future is ignored.
For example, in one test before this patch I see:
WARNING: exceptional future ignored: _Map_base::at
After this patch,
WARNING: exceptional future ignored of type 'std::out_of_range': _Map_base::at
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>