Patch to add missing PPC instruction

[degger@fhm.edu]

On 17 Dec, David Edelsohn wrote:

> 	fres is floating-point reciprocal ESTIMATE Single, not a
> single-precision reciprocal.

Right, I got that wrong.

> It is accurate to one part in either 256 or 4096, 

According to the PPC Programming Environment manual page 8-88,
the error is less or equal to 1/256.

> not IEEE 754 Single Precision accuracy. 

A candidate for -ffast-math? I originally meant it that way but forgot
about it between the time I wrote the patch and sent it here 
(>4 months).

For some applications (those who are using single precision arithmetics)
it might actually be enough to such an unaccurate reciprocal but I
definitely see your point when you say it's not acceptable to be used in 
general.

--
Servus,
       Daniel