SLATEC routines and bessel functions



I've finished checking in the Bessel routines and stuff, and I've
added some preliminary support for symbolic Bessel functions.

Here's a short transcript:

(C1) bessel_y[1](3.0);

(D1) 			        0.3246744247918
(C2) bessel_i[1](3.0);

(D2) 			       3.953370217402609
(C3) bessel_y[3/2](z);

					COS(z)	 SIN(z)
		       SQRT(2) SQRT(z) (------ - ------)
					  z	    2
						   z
(D3) 		       ---------------------------------
				   SQRT(%PI)
(C4) bessel_j[3/2](z);

					 COS(z)	  SIN(z)
			SQRT(2) SQRT(z) (------ - ------)
					   z	     2
						    z
(D4) 		      - ---------------------------------
				    SQRT(%PI)

It doesn't know about derivatives and such, but it should be easy to
add since maxima knows how to do that for %j.

Currently, Bessel functions of half-integral order are always expanded
out in terms of elementary functions.  Should there be a variable
controlling this?

Ray