Speedup!

[peter17]

Erik and I think that it should be possible to improve the speed by refactoring Pijnu.

Here are some tests performed on a Core 2 Duo @ 2 GHz:

• http://fr.wikipedia.org/wiki/Berceuse : ~ 6 s.
• http://fr.wikipedia.org/wiki/Shanghai : ~ 130 s. ; > 1.5 GB of RAM!

Erik pointed out that a lot of time is spent on the Recursive pattern. Maybe we can improve its speed and perhaps decrease a little its usage by adapting our patterns...