This involved changing a fair amount of code, rooted in how we access the local
IoFactory instance. I added a helper method to the rtio module to access the
optional local IoFactory. This is different than before in which it was assumed
that a local IoFactory was *always* present. Now, a separate io_error is raised
when an IoFactory is not present, yet I/O is requested.
We get a little more functionality from libuv for these kinds of streams (things
like terminal dimentions), and it also appears to more gracefully handle the
stream being a window. Beforehand, if you used stdio and hit CTRL+d on a
process, libuv would continually return 0-length successful reads instead of
interpreting that the stream was closed.
I was hoping to be able to write tests for this, but currently the testing
infrastructure doesn't allow tests with a stdin and a stdout, but this has been
manually tested! (not that it means much)
