Make 1995/cdua easier to see with modern systems

As modern systems are so much faster it's hard to see the maze being
solved in real time so I added a call to usleep() with a macro defined
in the Makefile (a macro in case someone finds it too slow or too fast
or wants to do some strange experiment like setting it to 40000 which I
actually tried). Called Z it defaults to 3000. To change it do something
like:

    make CFLAGS+="-DZ=1500" clobber all

To do this I had to remove the -include ... from the Makefile and
instead add the proper #includes to the source code as the += was not
concatenating to the CFLAGS.

This makes the entry a bit more enjoyable with current systems. There
still is a known issue that I'll look at again another time.

1995/cdua/Makefile

@@ -57,11 +57,11 @@ ARCH=
 
 # Defines that are needed to compile
 #
-CDEFINE=
+CDEFINE= -DZ=3000
 
 # Include files that are needed to compile
 #
-CINCLUDE= -include stdlib.h -include stdio.h
+CINCLUDE= 
 
 # Optimization
 #