Clean up Bessel functions
The files chen_bessel.f and bessel.F appear to be the same. It doesn't look like chen_bessel.f is in the make file. Could this be removed? I also noticed that this file might not be necessary: text file?
Also, bessel.i and chen_bessel.f only differ by one line: < # 1 "bessel.F"
Or am I missing something and these are necessary?