#6 Add cr and lf as separately printable characters

[Ryan Johnston]

Right now, it is possible to use crlf in the context of printing a carriage return line feed (or just a linefeed if you use SetFullCRLF). I would like to be able to print carriage returns and linefeeds separately and explicitly.

Using the attached version of PrintDriver (which just adds two elseif statements), I was able to do the following in the CLIPS repl:

$ ./clips
         CLIPS (6.4.1 4/8/23)
CLIPS> (println "Hello," lf "world!")
Hello,
world!
CLIPS> (println "Hello," cr "world!")
world!
CLIPS> (exit)

[Gary Riley]

Added.