export Why3's extended hash tables as Stdlib.XHashtbl
in order to keep OCaml's Hashtbl accessible. Unlike Stdlib.Map
which fully covers the OCaml's interface, Stdlib.XHashtbl does
not provide polymorphic hash tables.

Util now is a small module containing misc functions.

+ fix a bug in "compare"

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

+ add an explanation comment in src/util/stdlib.ml*

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

+ do not build src/programs/
+ build the library in lib/why3/
+ fix use_api.ml for the case when Alt-Ergo is not present
+ distribute lib/coq/BuiltIn.v
+ rename src/config to src/why3config
+ rename src/bench to src/why3bench
+ move src/config.ml to src/util/