WIP
Revert "WIP", taking Racket support in a different direction

This reverts commit 723f7fd2ad8da4bc1e9adfb1973846bff082727a.

Rather than re-write the whole book to work around differences between
Racket and other Schemes, mutable and immutable cons, etc, abandoning
Racket at least for these early chapters.
fix typo in chapter 1 test (?)

The interpreter in chapter 1 requires all variables to be created with
the macro `definitial`, and chap1.scm creates a lowercase "k" but not
an upper case "K", assume this was just a typo?
added supporting code for Racket (in R5RS mode)
added supporting code for Guile