Use 64-bit versions of stat, readdir and setrlimit functions when available

Use 64-bit versions of stat, readdir and setrlimit functions when available

strace already has a mechanism to use fopen64 for output when the 64-bit
version of fopen is available on 32-bit architectures.  Apply this
mechanism for other three functions to make strace fully adopted for
64-bit types.

* strace.c (struct_stat, stat_file, struct_dirent, read_dir,
struct_rlimit, set_rlimit): New macros.
(startup_attach): Use read_dir.
(startup_child): Use struct_stat and stat_file.
(main): Use struct_rlimit and set_rlimit.