and PredefEvalClock.

performed. The resulting code is both more compact, and more general.

It is more  general, since that predef operators  are now represented
by  node_exp_eff, exactly as  user nodes.   Hence, all  the functions
that were  operating on  user nodes via  node_exp_eff (such  as, node
aliasing) works for free on predef op!

In order to be able  to perform that generalisation, it was necessary
to  extend sligthly  the data  structure used  to represent  the node
profile in CompiledData.node_exp_eff with information indicating if a
variable is polymorphic or overloaded.

Not that, currently, polymorphic  or overloaded variables can only be
introduced by predef  operators. But I think it would  be easy to add
those notions for normal user nodes after this change.

New non-reg files boolred now compiles. Those involving
- boolred
- alias on predef.op

Also, node aliased to other nodes were handled poorly: I was replacing
in the syntax tree the node by its alias. Now, I really define
the alias node using the aliases one.

For instance,

    node toto(x:t) returns (y:t);
    let
      ...
     tel
     node titi = toto;
     node tutu(...) returns(...);
     let
        ...
	z = titi(a);
     tel

was compiled into

    node toto(x:t) returns (y:t);
    let
      ...
     tel

     node tutu(...) returns(...);
     let
        ...
	z = toto(a);
     tel

Now, I generate

     node toto(x:t) returns (y:t);
     let
       ...
     tel
     node titi(i1:t) returns (o1:t);
     let
       o1 =toto(i1);
     tel
     node tutu(...) returns(...);
     let
        ...
	z = titi(a);
     tel

which is equivalent, but closer to the original program.

(support for fill, red, etc. is coming soon).

In order to add support  for iterators, I have extended the by_pos_op
(and the by_pos_op_eff) data type with a list of static arguments. In
other words, iterators are handled as a particular case of predefined
operators.

not compile them is (well, was) the default...).

also, during pretty-printing, remove the type in the constant definition
(e.g., "const x = 42;" instead of "const x = 42:int;"), except if it is an abstract
constant of course

and anonymous structures. I've even found some type errors in the non-reg files!

operators. Predef contains the abstract syntax of those operators (taken
for SyntaxTreeCore.by_pos_op), and PredefSemantics contains:

 - const_eval: that says how to statically evaluate constants
 - type_eval: that provides the type profile of predef operators
 - clock_eval: that provides the clock profile of predef operators

The code in EvalConst that dealt with predef const evaluation is now in
Predef.const_eval