Generate an ELF /boot/loader instead of fake a.out. The fake a.out wrapper

did not work with old a.out-only bootblocks anyway. :-(

sys/boot/i386/loader/Makefile

@@ -81,7 +81,7 @@ vers.o:	${.CURDIR}/../../common/newvers.sh ${.CURDIR}/version
 	${CC} -c vers.c
 
 ${BASE}: ${BASE}.bin ${BTXLDR} ${BTXKERN} ${BTXCRT} ${BASE}.help
-	btxld -v -f aout -e ${LOADER_ADDRESS} -o ${.TARGET} -l ${BTXLDR} \
+	btxld -v -f elf -e ${LOADER_ADDRESS} -o ${.TARGET} -l ${BTXLDR} \
 		-b ${BTXKERN} ${BASE}.bin
 #	/usr/bin/kzip ${.TARGET}
 #	mv ${.TARGET}.kz ${.TARGET}