Make fiber_entry static

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65881 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

cont.c

@@ -819,7 +819,8 @@ cont_restore_thread(rb_context_t *cont)
 
 #if FIBER_USE_NATIVE
 #if defined(FIBER_USE_COROUTINE)
-COROUTINE fiber_entry(coroutine_context * from, coroutine_context * to)
+static COROUTINE
+fiber_entry(coroutine_context * from, coroutine_context * to)
 {
     rb_fiber_start();
 }