[Ada] Add switch to control warning on suspicious modulus

[Paolo Bonzini]

On 07/13/2009 10:23 AM, Arnaud Charlet wrote:
> This patch implements the switches -gnatw.m/w.M to turn
> the warning for suspicious modulus (cf previous patch) values on and off.
> Given the test program:
>
> package badmod2 is
>     type r is mod 32;
> end;
>
> If compiled with -gnatw.m or no switches, the following
> warning is generated:

It would be nice to have gnat.dg test for this.

Paolo