I restored part of documentation that describes what is a let-no-escape
and which was deleted 10 months ago together with the old codegen. Then
I removed lots of Literate Haskell clutter (like empty \begin{code} -
\end{code} blocks) and finally decided to remove all the Literate Haskell
markup because there wasn't much of it left, but it made comments so
difficult to read.