move rb_vm_lvar_exposed() correctly.

rb_vm_lvar_exposed() is prepared for __builtin_inline!(), needed for
mini_builtin.c and builtin.c. However, it's only on builtin.c.
So move it to make it as a part of VM.

Author: ko1

builtin.c

@@ -41,11 +41,3 @@ Init_builtin(void)
 {
     //
 }
-
-// inline
-VALUE
-rb_vm_lvar_exposed(rb_execution_context_t *ec, int index)
-{
-    const rb_control_frame_t *cfp = ec->cfp;
-    return cfp->ep[index];
-}

vm_insnhelper.c

@@ -4995,3 +4995,12 @@ vm_invoke_builtin_delegate(rb_execution_context_t *ec, rb_control_frame_t *cfp,
     // fprintf(stderr, "%s %s(%d):%p\n", __func__, bf->name, bf->argc, bf->func_ptr);
     return invoke_bf(ec, cfp, bf, argv);
 }
+
+// for __builtin_inline!()
+
+VALUE
+rb_vm_lvar_exposed(rb_execution_context_t *ec, int index)
+{
+    const rb_control_frame_t *cfp = ec->cfp;
+    return cfp->ep[index];
+}