Add O_NOINHERIT

[headius]

O_NOINHERIT is the Windows equivalent of O_CLOEXEC. In order to start using O_NOINHERIT in JRuby, I need this constant added (and generated) for all backends (fake, xplatform, platform).

Should just be a matter of adding it and generating fake, xplatform, and at least Windows platform.

I'll get to it in the morning, perhaps.