Most bessel functions do not preserve input type

[denizyuret]

julia> x                                                                                                                                                     
0.22919536f0                                                                                                                                                 
                                                                                                                                                             
julia> besseli(2,x)                                                                                                                                          
0.006595105469050567                                                                                                                                         

[PaulXiCao]

I will look into this. See pr #234 (is currently a draft)