big: add random number generation

[FlorianUekermann]

A random number generator returning equally distributed big.Int values between 0 and n
(like rands Intn(int) method) would be nice and usefull.

Implementing them outside the big Package would be possible but since the relevant
fields of big.Int are private, there is no really elegant and efficient way to do this
as far as I can see.

And since these are very basic operations which may often be usefull when dealing with
"big" numbers it would be a good idea to have them provided by the standard
library anyway imho.

If you like this idea but don't have time to implement it yourself, just give me some
hints how you would like it to be structured, since I need to do it anyway.

[adg]

Comment 1:

Labels changed: added featurerequest, priority-low, removed priority-medium.

Status changed to HelpWanted.

[rsc]

Comment 2:

The way to implement this is to wrap nat.random,
already in the big package and used by probablyPrime.

[rsc]

Comment 4:

changeset:   6551:721e204b1c38
user:        Florian Uekermann <florian@uekermann-online.de>
date:        Mon Oct 18 14:09:20 2010 -0400
summary:     big: add random number generation

Status changed to Fixed.