let.
* scheme-binding.texi (Internal Definitions): New explanation of
`Internal Definitions'.
(Top Level): Documented behaviour of top level definitions.
(Binding Constructs): New introductory text.
(Local Bindings): Explain concept of local bindings. Document
let, let* and letrec.
* scheme-modules.texi (Modules): Added menu descriptions.
(Scheme and modules, The Guile module system): Some whitespace
cleanup
(The Guile module system): Layout fixes, docstring fix for
`define-module'.
