test_fileutil: fix signedness warnings
test_fileutil: fix signedness warnings

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