[racket] Running Racket in the R6RS mode

Thank you, Matthias (and also Neil Van Dyke) for the very
detailed explanation of the design decisions that has gone
into Racket.  Now I see that Racket is intended to be a Lisp
dialect of its own rather than a "Scheme plus extensions"
as I had mistakenly assumed.

In retrospect, that assumption was influenced by my experience
with C which is the predominant language in which I program.
Various implementations of C, such as those of GNU, Microsoft,
Intel, Sun, AIX, etc., provide their own diverse extensions
to the language but in all cases the extensions are strict
supersets of the standard C -- they would be considered
unacceptable otherwise.

I was looking for something similar in the scheme world but
what I have learned is that one cannot extend his experience
from one programming language realm and culture into another
and expect to find a one to one correspondence.

At any rate, racket seems to be a well-thought-out product
and I intend to look more into it.

Rouben