[Matrix-SIG] Updated cephes module for non-Linux

[Travis E. Oliphant]

I've recently updated cephes module to fix some installation problems on
platforms besides PC's.  Thanks to Jim Boyle for pointing them out.

Changes:

  -- eliminated log2 function.
  -- better INSTALL help
  -- changed so gamma works with Solaris math library.

I've compiled and tested the library on IRIX-6.2 and SunOS-5.6
This is a cross-platform improvement upgrade only.

Linux users get no benefit from the change.

----------------------------------------------------
Travis Oliphant            200 First St SW          
    	                   Rochester MN 55905       
Ultrasound Research Lab	   (507) 286-5923           
Mayo Graduate School	   Oliphant.Travis@mayo.edu