test/Makefile: cleanup
test/Makefile: cleanup

* regtest_compat is now EXTRA target
* regtest_system is built against libusual.a

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