c++/4512: New ICE in loop_iterations at unroll.c:3510, regression vs. 3.0.1

[Mark Mitchell]

> The appended patch fixes that and makes the code compile. Currently
> bootstrapping on PPC and x86.

All right, I take it back.  This version I find so utterly convincing
I'm willing to risk making a complete fool of myself.

After your tests, please unrevert my reversion, and apply this patch
in addition.  Then let me know.

At that point, I want to (finally) spin a prerelease.

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com