Fix 2020/ferguson1/Makefile

The DATA variable still had html files which I removed a while back.
This made make fail.

Also there is a joke Easter egg that I added: something to do with
eating as that's also kind of the point of the entry: though eating
insects (or bugs for a joke I made originally, so that it can say there
are bugs that are not bugs). Snakes are carnivores: they don't eat
apples and although insects are not going to be filling enough they can
eat them. But what the joke is one has to discover for themselves!

2020/ferguson1/.gitignore

@@ -8,6 +8,7 @@ play
 prog
 prog.alt
 prog.orig
+sandwich
 snake
 snake.alt
 snake-colours

2020/ferguson1/Makefile

@@ -114,11 +114,11 @@ ENTRY= ferguson1
 PROG= prog
 #
 OBJ= ${PROG}.o
-DATA= COMPILING.md HACKING.md bugs.html bugs.md cake.jpg cannibalism.log.md \
-	chocolate-cake.html chocolate-cake.md crazy.log.md gameplay.html gameplay.md \
+DATA= COMPILING.md HACKING.md bugs.md cake.jpg cannibalism.log.md \
+	chocolate-cake.md crazy.log.md gameplay.md \
 	halfwidth_vs_fullwidth.png ioccc-cake.jpg play.sh prog.2.c prog.3-j.c \
-	prog.3.c snake-colours.sh snake.1 spoilers.html spoilers.md \
-	termcaps.c terminals.html terminals.md troubleshooting.html troubleshooting.md
+	prog.3.c snake-colours.sh snake.1  spoilers.md \
+	termcaps.c terminals.md troubleshooting.md
 TARGET= ${PROG} termcaps play snake-colours
 #
 ALT_OBJ= ${PROG}.alt.o
@@ -139,6 +139,7 @@ all: data ${TARGET}
 
 ${PROG}: ${PROG}.c
 	${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
+	@${TOUCH} sandwich
 
 # termcaps - test utility for terminal capabilities, size etc.
 termcaps: termcaps.c