FreeBSD: use stat header in freebsd11/freebsd12 on aarch64

sys/stat.h is a machine-independent header, but it has ifdefs for i386.
The version that was called x86_64.rs should be used on powerpc64 too,
but I don't have a machine to test that on.

src/unix/bsd/freebsdlike/freebsd/aarch64.rs

@@ -4,32 +4,6 @@ pub type c_ulong = u64;
 pub type time_t = i64;
 pub type suseconds_t = i64;
 
-s! {
-    pub struct stat {
-        pub st_dev: ::dev_t,
-        pub st_ino: ::ino_t,
-        pub st_mode: ::mode_t,
-        pub st_nlink: ::nlink_t,
-        pub st_uid: ::uid_t,
-        pub st_gid: ::gid_t,
-        pub st_rdev: ::dev_t,
-        pub st_atime: ::time_t,
-        pub st_atime_nsec: ::c_long,
-        pub st_mtime: ::time_t,
-        pub st_mtime_nsec: ::c_long,
-        pub st_ctime: ::time_t,
-        pub st_ctime_nsec: ::c_long,
-        pub st_size: ::off_t,
-        pub st_blocks: ::blkcnt_t,
-        pub st_blksize: ::blksize_t,
-        pub st_flags: ::fflags_t,
-        pub st_gen: u32,
-        pub st_lspare: i32,
-        pub st_birthtime: ::time_t,
-        pub st_birthtime_nsec: ::c_long,
-    }
-}
-
 // should be pub(crate), but that requires Rust 1.18.0
 cfg_if! {
     if #[cfg(libc_const_size_of)] {

src/unix/bsd/freebsdlike/freebsd/freebsd11/mod.rs

@@ -217,8 +217,9 @@ extern "C" {
 }
 
 cfg_if! {
-    if #[cfg(target_arch = "x86_64")] {
-        mod x86_64;
-        pub use self::x86_64::*;
+    if #[cfg(any(target_arch = "x86_64",
+                 target_arch = "aarch64"))] {
+        mod b64;
+        pub use self::b64::*;
     }
 }

src/unix/bsd/freebsdlike/freebsd/freebsd12/mod.rs

@@ -217,8 +217,9 @@ extern "C" {
 }
 
 cfg_if! {
-    if #[cfg(target_arch = "x86_64")] {
-        mod x86_64;
-        pub use self::x86_64::*;
+    if #[cfg(any(target_arch = "x86_64",
+                 target_arch = "aarch64"))] {
+        mod b64;
+        pub use self::b64::*;
     }
 }