Remove a lot of warnings (considered as errors by dune).

Indeed, expressions such as "3.0-42.5" caused a syntax error, as the unary minus
of real constant was in hard in the lexer.  "3.0- 42.5" worked, but still.

The problem then was that LicEvalConst refused to eval "- 3.14", that was
parsed directly as a constant, and that is now a call to the unary minus.
I've added specific code to handle this case.

- add a sectiuon on operators priority
- fix the automatic latex grammar generator (now calles yacc2latex)

also force the -rif in the utils/luciole-rif script when used with
lutin or lus2lic.

Currently no integrity check is performed (i.e., check that each node
that uses an unsafe node is itself declared as unsafe).

As far as ldbg is concerned, it only traces the toplevel node, at
call event.

Note that I needed to rename quite a lot of modules to avoid name clashes
between lus2lic.a and ltop.

I've also merged the Verbose module with the one of Lutin so that
they can be shared (there were sharing 95% already).

nb : do not work for lv4/ec mode

including files) was wrong (well, at least, too restrictive, numbers
were forbidden in file names...).

Add a -tlex option to debug the lexer.

Also, rename the rules in parser.mly now that their appear in the manual.
This renaming work is in progress though.

by position). Rename ExpandPack into InstanciateModel.

before '..'.

For non-regression tests, do not use Lazycompiler.test function
anymore and just use  LazyCompiler.node_check instead.

put in the new file compiledDataDump.ml all the stuff
related to string convertions of CompiledData items.

around a lexing bug that I don't know how to fix yet.

Add Some lustre files that are automatically tested thanks to the
generic Makefile (from the Youssef compiler).

Test files are organized as follows :

 - files in directories that are under the "should_fail" directory
  do triggers errors, but it is intented

	should_fail/syntax
	should_fail/type
	should_fail/semantics

 - and files that should not trigger any error:

	should_work/

To do that, we :

(1) totally remove  (in the  ocaml code) the  use of "oper",  and use
"node" instead.  Indeed, a node  is a memoryfull operator, as opposed
to function that are memoryless operators.  However, lus2lic does not
really care about memoryless  and memoryfull information. Therefore I
prefer  to use  node everywhere,  and to  flag node_info  to indicate
whether it has memories or not.

(2) change the syntaxTreeCore type to make it more general. Indeed,
    the distinction between functions and nodes was

    - redundant:  extern nodes  and (extern)  functions  were handled
    differently (NodeExtern versus ExtNode (was named FUNC before)).

    - and  incomplete:   it  was  not  possible   to  provide  static
      parameters to function, nor to define functions with body, etc.

Now a  function is  just a memoryless  node. The check  that function
indeed use no memory will be done later.

(3) also,  change  the  parser   so  that  functions  with  body  are
    accepted.

(4) in order  to do it step by  step, I add the  "extern" keyword" so
    that extern nodes and functions are more easy to parse. I will
    remove it later.

	ident where not authorized to begin by "_"...

Add basic regression tests.

Add "assert false" statements everywhere it was necessary.

Add the fby operator in the syntax.