IF macro

[BEE at MIT-MC (Bruce E. Edwards)]

I do not in general like the syntax of the if with the keyword ELSE.
I find IF marginally useful, because usually I have more than one thing
to do in one of the clauses, however, when I only have one thing to
do, it is clear (at least to me) that IF is the right thing. I therefore
think that it should be included, and also flamed about, just like
backquote.