Chi square test for variance

[parisse]

Xcas has the following commands for tests:
- chisquaret (chi2 test)
- normalt (normal)
- studentt (Student)
- kolmogorovt (K.-Smirnov)
- wilcoxont (Wilcoxon)

chisquaret takes 2 args: 2 samples or 1 sample and a distribution law (i.e. you can test adequation with more distributions than just the normal distribution).

I don't think these commands are inside the Prime right now, might be an interesting addition...