Bessel functions



I'm adding a few corrections and enhancements to the Bessel functions,
but before I do, I wanted some opinions.

Currently, bessel_j(1,2) will produce a numerical result.  Contrast
this with, say, sin(2), which doesn't.  Should bessel_j do the same?

Also, there exists the function BESSEL(arg, order), which, perversely,
is exactly the same as BESSEL_J, but with its args in the reverse
order.  Can we just get rid of BESSEL altogether in favor of bessel_j?

Ray