[commit/Ada] delete ada-lang.c:extract_string and use target_read_string instead

[Tom Tromey]

>>>>> "Joel" == Joel Brobecker <brobecker@adacore.com> writes:

Joel> +      xfree (main_program_name);
Joel> +      target_read_string (main_program_name_addr, &main_program_name,
Joel> +                          1024, &err_code);
Joel> +
Joel> +      if (err_code != 0)
Joel> +        return NULL;
Joel>        return main_program_name;

I don't know what the Ada compiler emits here, but offhand it seems
like this needs a conversion to the host charset.

I'd imagine in most cases everything is ASCII-compatible and therefore
the problem never manifests.

Tom