Close simgrid/simgrid#43 on framagit, and update ChangeLog.

Close simgrid/simgrid#43 on framagit, and update ChangeLog.

Concerns have been addressed by commits:
a5a63cee9b Redraw if the random number is too close to max, to avoid modulo bias
fbf0f42532 Documenting xbt/random a little bit
037217ec21 Exclude max from range for xbt::random::uniform_real.