replace trailing whitespace with blackslash in README.md

As an alternative to the markdown trailing whitespace as a line
break, we use a trailing blackslash as a markdown line break.

1998/fanf/README.md

@@ -10,7 +10,7 @@ United Kingdom
 make all
 ```
 
-NOTE: This may take a while.  Some systems may have problems building 
+NOTE: This may take a while.  Some systems may have problems building\
 this entry because of the system resources it requires.
 
 ## To run: