rt: Remove rust_refcount.h

Author: brson

src/rt/rust_refcount.h

@@ -13,7 +13,6 @@
 #define RUST_TYPE_H
 
 #include "rust_globals.h"
-#include "rust_refcount.h"
 
 struct rust_opaque_box;
 
@@ -28,6 +27,8 @@ struct type_desc;
 typedef void CDECL (glue_fn)(void *,
                              void *);
 
+typedef unsigned long ref_cnt_t;
+
 // Corresponds to the boxed data in the @ region.  The body follows the
 // header; you can obtain a ptr via box_body() below.
 struct rust_opaque_box {