makefile: make config.h installable again
makefile: make config.h installable again

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