Submitted by Johannes Kanig

this is useful to declare on-the-fly a new sort which replaces
a complex type. Otherwise, the printer has to traverse any term
twice: first, to detect complex types, second, to print the term.

also, avoid the "encoding_sort" transformation, if it can be done
directly in the printer.

On the same example as in the previous commits, this gives 5x
acceleration together with some memory usage reduction.

we still keep bv_vars in the binders, so calculating the set
of free variables only has to descend to the topmost binders.
The difference on an example from BWare is quite striking:

/usr/bin/time why3-replayer : with t_vars

505.14user 15.58system 8:40.45elapsed 100%CPU (0avgtext+0avgdata 3140336maxresident)k

/usr/bin/time why3-replayer : without t_vars

242.96user 12.04system 4:16.31elapsed 99%CPU (0avgtext+0avgdata 2007184maxresident)k

Not only we take 2/3 of memory, but we also gain in speed (less work
for the GC, most probably).

This patch should be tested on big WhyML examples,
since src/whyml/mlw_*.ml are big users of t_vars.

Thanks to Guillaume for the suggestion.

(inspired from patches provided by Piotr Trojanek)

Util now is a small module containing misc functions.

+ rename Debug.Opt to Debug.Args to avoid conflicts

+ create AUTHORS file
+ fix the linking exception in LICENSE
+ update the "About" in IDE
+ remove the trailing whitespace
+ inflate my scores at Ohloh

For realization, code extraction, metas-in-sessions, etc, we need
absolute names for identifiers. To that purpose it is better to
have and store the qualified path to every ident.

 (metas, debug flags, transformations, formats) except for label.

This description is used in --list-*. The description can use any of
the formatting markup of Format "@ " "@[",...

Transformations can also specify from which metas and labels they
depend, and add informations about how they are interpreted.

TODO:
  - complete and correct the documentation
  - when a transformation use Trans.on_meta, it should be possible to
    add an interpretation of the metas in the documentation.
  - recover a summary version of --list-* ?
  - be able to export in latex?

- put abstract types and aliases in Dtype of tysymbol
- put (recursive) algebraic types in Ddata of (ts,constr list) list
- put abstract function/predicate symbols in Dparam of lsymbol
- put defined logic symbols in Dlogic of (ls,ls_definition) list

also, produce less noise on plugin detection
also, use -linkall to compile our binaries

Why3 library mechanism is not adapted for forward dependencies.

- change takes function as the first argument
- add_new takes exception as the first argument
- find_default is renamed to find_def and takes the default value
  as the first argument
- find_option is renamed to find_opt (to align with find_exn and find_def)
- default_option is renamed def_option