signal: separate sigval from sigevent
signal: separate sigval from sigevent

On OpenBSD sigval is defined but sigevent is not.

Tie sigval with siginfo's SI_QUEUE.

Reported-by: Pierre-Emmanuel André

ifduyue/libusual,rabbitt/libusual,mgjv/libusual,ifduyue/libusual,markokr/libusual,mgjv/libusual,ifduyue/libusual,mgjv/libusual,mgjv/libusual,rabbitt/libusual,rabbitt/libusual,ifduyue/libusual,markokr/libusual,markokr/libusual,rabbitt/libusual,markokr/libusual