We had a failing spec where a thread blocked on read was
supposed to raise IOError when *another thread* closed
the IO. However, it didn't work. Turns out that the
low-level system read function blocks forever so the
closed IO/file descriptor didn't raise as expected.

The original C code got around this OS behavior by setting
special flags and sending signals to the blocked thread
to wake it up. This mechanism was only exposed to the
bytecode VM and wasn't available to the Ruby runtime so
I had to go this other direction. It's less than ideal
but if the long-term plan is to utilize libuv for
Rubinius IO then this is a good enough fix.