Flocq

Version using extraction of Flocq

It is used quite differently from the current master:

• Renamed "F" to "Farith" because I think it is not a good practice to not take such toplevel short name.
• The floating points have an arbitrary size but fixed
• To get the same use than master one can do the computation using operation on Q.t and do the rounding with Farith.D.roundq : mw:int -> ew:int -> mode -> Q.t -> Q.t