[gfortran] Commit a workaround for PR 29516

[Brooks Moses]

François-Xavier Coudert wrote:
> I intend to commit the following workaround for PR 29516
> (trans-array.c getting miscompiled on i686-darwin) to mainline and
> 4.2, unless someone objects.
> 
> Of course, we'd better have someone fix the original bug, but it
> doesn't look like it's going to happen soon :)
> 
> Bootstrapped and regtested on i686-linux. It does clear the testsuite
> for i686-darwin.

Personally, I would suggest putting a "TODO:" in the comment, to enhance 
the chances that the workaround will get removed someday once the bug is 
fixed.

- Brooks