whiteknight/io_cleanup1 branch, ready to merge

[Andrew Whitworth]

After a few commits yesterday, it appears the last few remaining
issues with the whiteknight/io_cleanup1 branch are resolved and it is
ready to merge. Moritz++ has tested Rakudo and a few modules
especially LWP::Simple and Http::Client. He claims he sees no
regressions (with one small patch applied to Rakudo).

I would like to merge this branch today. More testing would be
appreciated. Please let me know ASAP if anybody has any questions or
concerns.

Thanks,

--Andrew Whitworth