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/README.md

@@ -1,27 +1,37 @@
 # Best Output
 
-    Carlos Duarte
-    Instituto Superior Tecnico
-    Largo da Igreja, 5 R/C DTo
-    Damaia
-    2720 Amadora 
-    Portugal
+Carlos Duarte  
+Instituto Superior Tecnico  
+Largo da Igreja, 5 R/C DTo  
+Damaia  
+2720 Amadora   
+Portugal  
 
 ## To build:
 
-        make all
+```sh
+make all
+```
 
 [Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed this so that it
 would work with macOS. Once it could compile it additionally segfaulted under
 macOS which he also fixed. Thank you Cody for your assistance!
 
+NOTE: on modern systems this was hard to see it solve it in real time because it
+goes so quickly so Cody added a macro `Z` defaulting to 3000 for a call to
+`usleep()` to make it easier to see. The `Z` macro lets you configure it in case
+you find it too slow or too fast. To do that:
 
-## To run
+```sh
+make CFLAGS+="-DZ=1500" clobber all
+```
 
-	./cdua
+## To run:
+
+```sh
+./cdua
+```
 
-NOTE: on modern systems this might be hard to see it solve it in running time as
-it goes so quickly but it will still show the result after execution.
 
 NOTE: sometimes the program needs you to press enter a second time to continue
 solving the maze. See [bugs.md](/bugs.md) for more details.