Integer overflow causes incorrect output from bessel_deriv_zero_asymptotic

[simonp0420]

Here is an example of erroneous output when nu isa Int but correct output when nu isa Float64 of the same value:

julia> besselj_deriv_zero(37, 1)
0.0

julia> besselj_deriv_zero(37.0, 1)
39.71488992674072

The problem can be traced to integer overflow when computing the numerator of variable t4 in function bessel_deriv_zero_asymptotic. A similar problem with overflow occurs when computing the numerator of variable t4 in function bessel_zero_asymptotic, though it doesn't manifest until larger values of nu are used:

julia> FunctionZeros.besselj_zero_asymptotic(87, 1)
103.5246288334123

julia> FunctionZeros.besselj_zero_asymptotic(87.0, 1)
100.99682928339313

This error doesn't propagate out of besselj_zero because the erroneous asymptotic value is still close enough to the true zero for the latter to be found by the rootfinder.

I think that the solution is to promote nu to float(abs(nu_in)) whenever nu_in is an Integer. I'll work on a PR that implements this.