this commit will change the scale of values produced by fbm2d. This will
probably not happen again. As a consequence, fbm values will always be
constrained between -1 and 1, but do not perfectly stick to that scale.
There is no easy solution, if the user wants the best dynamic between -1
and 1, he should adjust manually the value by multiplying by a gain slightly superior to 1.
Former-commit-id: ebdba9e9f4bbb972abe355c07ec9f8bce42329b9
Remi Beges