polymorphic operators.

For instance, when LicDumping expression such as

    map<<map<<+,4>>,5>>

an  alias  node was  created  for  "map<<+,4>>"  (to unnest  iterator
calls). Fut this node is intrically overloaded (polymorphic). In this
change, we  look at  the type this  innr call  is used to  generate a
specialised (mono-morphic) version of the node alias.

Note that we currently still generate type variable when users write

     node mymap = map<<+,4>>;

The  idea  is  the  following:  each  time  a  nested  iterator  call
(map<<map<<n,3>>,4>>) is  encountered, we  create a fresh  alias name
(create_alias_name) ad we  add it in the node_alias_tbl.   At the end
of the  compilation, LicDump.dump_node_alias is  called, which prints
the definition of those node aliases.

For example, the expression  "map<<map<<n,3>>,4>>" is printed like this:

    map<<_node_alias1, 4>>

and later, the node alias is defined:

    node _node_alias1(x:int) returns(y:int); let y = map<<n,3>>(x); tel;

iterators (e.g.,  "Lustre::plus" instead of "Lustre::+")  in order to
make the life of lic3loc easier.

Not yet implemented (assert false): iterators, struct

Add a UnifyClock module, and rename Unify into UnifyType.

nb : a lot of test are now broken, because
   - the clock checking is now plugged ;-)
   - iterators, struct are not yet implemented

It  does not  work, I  have changed  my mind  to use  a  more general
clocking algorithm based on  unification. I commit that current state
just in case I change my mind again...

type_eff_ext into type_eff btw). The  rationale is to be able to type
alias           on           polymorphic          nodes           (cf
test/should_fail/semantics/bad_call03.lus,  that now  have  a correct
error msg).  It also makes  to code more compact (no more translation
from one  to the  other), and more  general (type_eff_ext  being more
general than type_eff).  User polymorphic nodes should be easy now.

move all the code in parsey.mly into parserUtil.ml (ease the debug).

equations is not done at all yet). Also, print the clock decorations
(when clk) in the generated file.

and PredefEvalClock.