Create skeleton implementation framework for Scheme libraries

- Scheme base library (equality, number, boolean, list, symbol,
  char, string, vector, bytevector, control, exception, io, system)
- Scheme case-lambda library (lambda)
- Scheme char library (char)
- Scheme complex library (complex)
- Scheme cxr library (cxr)
- Scheme eval library (eval)
- Scheme file library (file)
- Scheme inexact library (inexact)
- Scheme lazy library (lazy)
- Scheme load library (load)
- Scheme process-context library (context)
- Scheme read library (read)
- Scheme repl library (repl)
- Scheme time library (time)
- Scheme write library (write)