Gimplilfy ICE in gnat.dg/array18.adb

[Eric Botcazou]

> strangely my var_decl for 'a' is a record and not an array_type so the 'if'
> condition is false (and true on X86_64).... I looked for somewhere in my
> backend something that would transform an array_type into a record_type but
> I did not find anything.

The comment should clearly state the intent of the change though and how to 
adjust it to your needs.

-- 
Eric Botcazou