[Foxtrot] Some changes

[Alan Lawrence]

OK....

(1) sorted the primality test by removing the APR-CL bits. What we have
left is often (though not always) deterministic for numbers less than 100
digits or so anyway, so should be pretty good.

(2) Added the prime power test. Matt/Sharum, can you test this by
submitting to the server some numbers which are just powers of some of the
primes (those > 2^24) in TestUtils, please?

(3) changing mode should now work ok, i.e. change the mode for any
subsequent jobs.


Anything else needs doing (scrolling of status messages, GUI window in top
corner, etc.), please submit bug reports!!

Cheers,
Alan