add p_name field in kinfo_proc struct on OpenBSD

pthread_get_name_np() and pthread_set_name_np() are now using a kernel storage 
and could be viewed from outside the process.

Reference: openbsd/src@cef5a14

src/unix/bsd/netbsdlike/openbsd/mod.rs

@@ -498,6 +498,7 @@ s! {
         pub p_tid: i32,
         pub p_rtableid: u32,
         pub p_pledge: u64,
+        pub p_name: [::c_char; KI_MAXCOMLEN as usize],
     }
 
     pub struct kinfo_vmentry {