Pull in datasift macos fixes

[benjamg]

@glaude made the following changes to support OSx MeltwaterArchive@ed2c07e

These work although really the POLL_IN / POLL_OUT constants should be replaced because POLL_IN and POLL_OUT are both fairly common macros and I have no idea what I was thinking when I used them. Surprised it works anywhere.

This will of course break backwards compatibility

[dkick]

I really really really don't understand why people continue to SCREAM_THE_NAMES_OF_CONSTANTS like we're all still using the C preprocessor ...