"exact" calculator

[Hans Boehm]

I replaced the object version of the "exact" reals calculator in
titan.rice.edu:~ftp/sun-source/calc.shar.*  .  It is now divided into only
three pieces.  As before, it performs demand-driven calculation on the
reals, always insuring accurate results to whatever precision is displayed
on the screen.  Given the expression

		    ln((PI + e**(-500)) - PI)

it produces -500.  It still has a curses based user interface (functional
but not very pretty).  Changes include:

1. A number of glitches in the user interface were fixed.

2. A man page (largely contributed by R. P. C. Rodgers) is now included.
   A calculator icon is included.

3. Window resizes work under X as well as under Sunview.

4. Integer factorials and Solovay-Strassen primality testing were added.

5. It can be built under, and runs correctly under 4.0.  (It runs only on
   Sun 3s, but essentially no functionality is lost if it is run over the
   network.)