Hello again, I have added a :prologue param to the scheme blocks of babel.
This multiple option prepends all the values in the generated code of the
block.

This patch also includes the previous one that enabled returning a table
when evaluating a scheme block.

A changelog:

Enhance the babel block for scheme.

Allows scheme code blocks to return a table and add a :prologue param
to the scheme blocks. All :prologue params are prepended to the
body of code.

* lisp/ob-scheme.el (org-babel-scheme-null-to): New custom option that
  allows to use a empty list to format the table output, initially
  assigned to 'hlines.
  (org-babel-scheme-table-or-string): New helper function to convert
  the return value from the block as a table or a string.
  (org-babel-execute-src-block): Changed to allow the return of a
  table for the output.
  (org-babel-expand-body:scheme) Add :prologue param support.

The patch: