sizes.c.tmpl: prototype

* template/sizes.c.tmpl (Init_limits): turned a K&R style
  declaration into a prototype declaration.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60065 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

template/sizes.c.tmpl

@@ -25,10 +25,10 @@ conditions = {
 #endif
 
 % end
+extern void Init_limits(void);
 void
 Init_sizeof(void)
 {
-    extern void Init_limits();
     VALUE s = rb_hash_new();
     rb_define_const(rb_define_module("RbConfig"), "SIZEOF", s);