add inline specifier to frequently called functions

- entry_deleted_p(): hash.c
- ensure_block(): vm.c

src/hash.c

@@ -382,7 +382,7 @@ obj_eql(mrb_state *mrb, mrb_value a, mrb_value b, struct RHash *h)
   }
 }
 
-static mrb_bool
+static inline mrb_bool
 entry_deleted_p(const hash_entry* entry)
 {
   return mrb_undef_p(entry->key);

src/vm.c

@@ -609,7 +609,7 @@ funcall_args_capture(mrb_state *mrb, int stoff, mrb_int argc, const mrb_value *a
   }
 }
 
-static mrb_value
+static inline mrb_value
 ensure_block(mrb_state *mrb, mrb_value blk)
 {
   if (!mrb_nil_p(blk) && !mrb_proc_p(blk)) {