Rename all *.mit files to *.scm.
Rename all *.bgl files to *.scm.
Rename ChangeLog to ChangeLog.orig.

The ChangeLog file only contains changes from the original
author (Christian Queinnec). See the git log for any changes local to
this repo.
Add newline after printing value in chapter4-interpreter loop.
Fix typo in transcode: rename c -> v.
Initialize vars with create-number, not raw scheme integers.

This allows the user to drop into (chapter4-interpreter), and
immediately run (set! foo 42) or similar without getting an error.

The previous version would generate a type error in transcode-back,
since new2-evaluate-set! returns the previous value of the variable
being set, which in this case was a regular scheme int, 0, which caused
transcode-back to choke on the value when it attempted to send it the
'type message.
Improve display-exception by calling display-error.
fixup! Improve display-exception by calling display-error.
Add scheme4a to run an interpreter with the chap4a evaluate.

This is similar to the chapter4-interpreter, but sets wrong to handle
errors.
Fix a bug in evaluate-application: (car *v) -> f.