Add it.remap

[DBraun]

Linear remap function like many other libraries: https://processing.org/reference/map_.html

I'm open to any kind of refactoring.

[sletz]

Finally keeping the simpler version in https://github.com/grame-cncm/faustlibraries/commit/5ce55bbea7793c524a055ec61115b386eeba4588.