Move usleep() version of 1995/cdua to cdua.alt.c

This is to both preserve the original code (notwithstanding the bug
fixes I made) and also to allow you to compare the two versions. I now
have played with even slower values and I recommended trying it to see
different results in the README.md (which of course describes the alt
code, how to use it and reconfigure it etc.).

It's encouraged to use this version but it's also recommended to try the
original version as well.

Updated Makefile to do this. This reinstates the -include stdio.h
-include unistd.h in CINCLUDE but the -DZ=3000 is still in the CDEFINE
variable.  Why? It doesn't hurt having it in the cdua.c compilation and
it makes it easier to find. The cdua.alt.c still uses #include
directives so that redefining CFLAGS at compilation does not cause any
problems.

Thank you Landon for recommending that it's moved to an alt version; I
had thought of it but did not do it and this is much, much better!

1995/cdua/Makefile

@@ -61,7 +61,7 @@ CDEFINE= -DZ=3000
 
 # Include files that are needed to compile
 #
-CINCLUDE= 
+CINCLUDE= -include stdio.h -include stdlib.h
 
 # Optimization
 #
@@ -112,8 +112,8 @@ OBJ= ${PROG}.o
 DATA=
 TARGET= ${PROG}
 #
-ALT_OBJ=
-ALT_TARGET=
+ALT_OBJ= ${PROG}.alt.o
+ALT_TARGET= ${PROG}.alt
 
 
 #################
@@ -135,6 +135,10 @@ ${PROG}: ${PROG}.c
 alt: data ${ALT_TARGET}
 	@${TRUE}
 
+${ALT_TARGET}: ${PROG}.alt.c
+	${CC} ${CFLAGS} $< -o $@ ${LIBS}
+
+
 # data files
 #
 data: ${DATA}