fix aix -fcprop-register miscompilation

[John David Anglin]

> > 	* regrename.c (copy_value): Ignore overlapping copies.
> 
> This seems to fix 950704-1.c at -O1.  I will have the complete test results

Bootstrapped and checked.  Test results with the above patch are identical
to those from yesterday.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)