Improve my 1991/dds alt code (required for clang)

Based on a slight modification to the Makefile the program will now
compile to the same file as if dds.c was being used (a.out).

I updated the README.md with some changes in formatting to do with the
alt code but the file has not been fully corrected or even checked.

1991/dds/Makefile

@@ -133,7 +133,7 @@ ${PROG}: ${PROG}.c
 	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
 
 a: a.c
-	${CC} ${CFLAGS} -Wno-return-type $< -o $@ ${LDFLAGS}
+	${CC} ${CFLAGS} -Wno-return-type $< -o a.out ${LDFLAGS}
 
 # alternative executable
 #