remove `NON_SCALAR_THREAD_ID` support

`NON_SCALAR_THREAD_ID` shows `pthread_t` is non-scalar (non-pointer)
and only s390x is known platform. However, the supporting code is
very complex and it is only used for deubg print information.

So this patch removes the support of `NON_SCALAR_THREAD_ID`
and make the code simple.

1 files changed, 0 insertions, 2 deletions

diff --git a/vm_core.h b/vm_core.h
index f25b74dcdd..4de0777292 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -896,8 +896,6 @@ typedef struct rb_ensure_list {
     struct rb_ensure_entry entry;
 } rb_ensure_list_t;
 
-typedef char rb_thread_id_string_t[sizeof(rb_nativethread_id_t) * 2 + 3];
-
 typedef struct rb_fiber_struct rb_fiber_t;
 
 struct rb_waiting_list {