base_win32: remove duplicate sigval/sigevent declaration
base_win32: remove duplicate sigval/sigevent declaration

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