RList.filter using inner type repr by splitting modules

[remyzorg]

I splitted the modules sigs

DATA / DATA' S / S'

and also the functor Make. This is not visible for the outside.

The most important part of the code is filter_patch which propagates the new positions of the next patches when an insert is removed.

thanks to @vasilisp for help, advices and aslo guidance while splitting the modules...

[jrochel]

@remyzorg: What is the bug here ?