First test on display lists, times / 4...

- The paradigm actually is to make display list explicit.
- A new API could be done to hide them behind a « drawing API ».
- A new DisplayList class.
- A new TextDL display list and a new TextLayer that handles these
lists.
- These display lists encapsulate both graphic state and the MVP matrix.
- One can update either the display list graphics or the mvl
independently.
- Times on Android and desktop are very promising.
- We can certainly gain a lot more.
- Some micro-optimisations to avoid using methods where fields could be
used in critical sections (matrices for example).