Every semantic action stretch was already parenthesized by the lexer,
so this led only to redundant parentheses.

  which was always [false].
The field [stretch_raw_content] is still required (for ocamltypes) because
there is one place where we use it (a call to [stretch true] in printer.ml)
and it is NOT identical to [stretch_content] (there is padding and
parentheses). Perhaps one could find a way of removing it. For now
I'll just be dumb and leave it alone.

   If the programmer did not provide a name [_i] is used (where [i] is
   the producer's position in the right hand side).

   This syntax modification actually simplifies the code:
   - There is no more on-the-fly naming of unnamed arguments.
   - Inlining is no more restricted to semantic actions that do not use $i.

   The patch is large because:
   - This change has an impact on many modules.
   - The expected results of the bench had to be updated.

Action: Use [Set.of_list].

situation can actually happen.

A lot of cosmetic changes in order to avoid warnings (mostly unused variables).

git-svn-id: svn+ssh://scm.gforge.inria.fr/svnroot/menhir@320 0f8b5475-4b4e-0410-85a8-ee3154a6bfe7