Change callback signature to Ret(Args...)
Implement default forwarding in/out functions for sig forward
Fix mem leak in signals-test - use smart ptr
Don't use forward_as_tuple as its rvalue refs become invalid at the next
sequence point

Cleanup of debug msgs/removal of cout's
Do not use rvalue for variadic Args which is *not* type deduced in the
operator() context and was causing compile errors related to binding
lvalue/rvalue refs
Slight cleanup in signal; change sigfwd stuff in signal-test to assert tests