[Ada] fix bug in deferred constant

[Arnaud Charlet]

> In gfortran.dg, we use the dg-additional-sources directive to compile
> multiple source files for one test (we use it to have mixed C-Fortran
> testcases). As far as I can see, it has been there since 2003-06-05.
> See dg-additional-sources, dg-additional-files and
> dg-additional-files-options in gcc/testsuite/lib/gcc-defs.exp for
> details. Would it suit your purpose?

Possibly. Could someone show what one of the Ada test cases I posted
would look like using these options ? I'm not familiar enough with
dejagnu to be of much help here, but if there's a simple way to do
what we need, I'll be happy to follow it.

Arno