seeker, arith: add unary functions

nth_root: finds the n'th root of a number
power_no: raises given no to a particular power
Q_rsqrt: http://www.beyond3d.com/content/articles/8/
prime_num_chk: a very simple function, goes n iterations and x checks
               for a given number n (if prime)
               todo: have a look at pollard rho's algo or similar
                     and somehow find a way to fix it.
fibonacci_print: beautiful small code taken and reworked
factor_print: the same way a 7'th grader would do
              uses long double, to help us with the bigger numbers.
arith: remove unneeded code

this surfaced with factor_print not being able to take too
large numbers and causing trouble.
but now, we have used modf and long double to be able to take
a *sufficiently* large number the user can find.
arith: silence warnings with Q_rsqrt