New gdb.ada/repeat_dyn testcase.

New gdb.ada/repeat_dyn testcase.

This patch introduces a testcase that exercises a scenario
which used to trigger an internal-error, but no longer does:

Consider the following array:

   type Small is new Integer range Ident (1) .. Ident (10);
   type Table is array (1 .. 3) of Small;
   A1 : Table := (3, 5, 8);

The particularity of this array is that the type of each element
is a range type whose bounds are dynamic, since they depend on
the value returned by Ident (1) and Ident (10). Trying to apply
the repeat operator ('@') on one of its elements used to yield
an internal error:

    (gdb) p a1(1)@3
    $1 =
    /[...]/gdbtypes.c:4512: internal-error:
    copy_type: Assertion `TYPE_OBJFILE_OWNED (type)' failed.

Although the issue no longer appears, the testcase is still
interesting to have.

gdb/testsuite/ChangeLog:

        * gdb.ada/repeat_dyn: New testcase.

Tested on x86_64-linux with clean results.