porting unittest.py to Prothon.

I'm trying to port unittest.py to Prothon, here are my
impressions:

1. I realized that I don't know how to translate some
Python builtins. I mean either I haven't gained the knowledge
or the functionality is lacking. I decided to write a full
translation quick reference. See below.

2. Too many small changes during porting will be hard to
debug. It's better to make syntax changes first, import
Python functionality, run test suite and then moving in
small steps remove Python functionality. So I started
module pyCompat. Currently it is not usable because of
bug 37 in the interpreter (Mark, I sent you a private
message about that, have you got it?). It is also untested,
because testing depends on unittest.pr, which does't exist :)

3. There are minor incompatibilities between Prothon
and Python builtin objects, unless they are *all*
found and (documented or fixed) porting is a pain.

4. What is the status of "from Module import xxx"?

  -- Serge