hurd: Add missing struct __timeval for 64bit support

This is the same as linux_like/linux/gnu's __timeval for ut_tv for 64bit
architectures.

(backport <rust-lang#3786>)
(cherry picked from commit c8f2b3c)

src/unix/hurd/mod.rs

@@ -450,6 +450,11 @@ s! {
         pub tv_nsec: __syscall_slong_t,
     }
 
+    pub struct __timeval {
+        pub tv_sec: i32,
+        pub tv_usec: i32,
+    }
+
     pub struct __locale_data {
         pub _address: u8,
     }