Fix description of bug in 1990/westley

Add to README.md that one thing (a crash without an arg) is at this time
not a bug but a feature.

Fix the statement that a negative number causes the entry to enter an
infinite loop. Instead any input that's not a number > 0 will cause the
program to enter an infinite loop.

1990/westley/Makefile

@@ -128,6 +128,8 @@ all: data ${TARGET}
 	supernova deep_magic magic charon pluto
 
 ${PROG}: ${PROG}.c
+	@echo "NOTE: this will very likely crash without an arg and will enter an infinite loop"
+	@echo "with an arg that is not a number > 0."
 	${CC} ${CFLAGS} $< -o $@ ${LIBS}
 
 # alternative executable