Fix problem with constant modulus

[Eric Botcazou]

> Can you do some more debugging and see what's going on?
>
> There aren't that many divisions by constant non-powers of two in the
> compiler ...

Richard, I get a similar bootstrap failure (same location) when I pass 
i586-redhat-linux-gnu to the configure script:

stage2/xgcc -Bstage2/ -B/home/eric/gnat/local/i586-redhat-linux-gnu/bin/ -c 
-g -O2      -gnatpg -gnata -I- -I. -Iada -I../../gcc/ada 
../../gcc/ada/ada.ads -o ada/ada.o
+===========================GNAT BUG DETECTED==============================+
| 3.5.0 20040421 (experimental) (i586-redhat-linux-gnu) Storage_Error stack 
overflow (or erroneous memory access)|
| Error detected at ada.ads:17:14                                          |
| Please submit a bug report; see http://gcc.gnu.org/bugs.html.            |
| Include the entire contents of this bug box in the report.               |
| Include the exact gcc or gnatmake command that you entered.              |
| Also include sources listed below in gnatchop format                     |
| (concatenated together with no headers between files).                   |
+==========================================================================+

Hopefully they are related and you'll be able to reproduce this one more 
easily.

-- 
Eric Botcazou