From: Run Paint Run Run <runrun@...>
Date: 2010-12-16T22:56:45+09:00
Subject: [ruby-core:33751] Re: [Ruby 1.9-Feature#4038] IO#advise

> Please check-in, but I think symbol initialization (:normal etc.) is
> needed only when posix_fadvise(2) is available.

The advantage of the current approach is that we can fail earlier.
Otherwise, a script containing `io.advise([1,2,3])` would not raise an
exception under Windows, but would if run under Linux.