random number generators for calc

[tino]

Hi,

There are currently only uniform random number generators available in
calc, namely RAND() and RANDBETWEEN(...). I'd be interested in
generators for other distributions, like normal, exponential etc.

I'd suggest using boost/random.hpp and then implementation will be
straight forward. We could also replace rand()/(RAND_MAX+1) in RAND()
with a boost random generator (rand() under windows can be extremely
poorly implemented and only have 2^16 different values or so). This
would also solve this windows only bug:

 https://bugs.freedesktop.org/show_bug.cgi?id=33365

Opinions?

Cheers, Tino