Address complaints from gdb_ari.sh:

Address complaints from gdb_ari.sh:

* ada-exp.y: Include gdb_string.h rather than string.h.
(convert_char_literal): Reformat declaration.
* ada-lang.h: Include opaque struct declaration for struct frame_info.
* ada-lex.l: Change use of free to xfree (the macro would do so
anyway, but this is harmless).
Include gdb_string.h rather than string.h.
* ada-valprint.c (ada_val_print_stub): Change PTR => void*.

* ada-lang.c (parse): Remove K&Rism in parameter list.
(is_name_suffix): Correct Linux => GNU/Linux in comment.