I've checked in support for allowing CoreFoundation to manage IO in PollDeviceBackend, for systems so equipped (OSX, etc). I didn't add a query function, which was an oversight on my part.
void enable_core_foundation (int(0..1) enable); constant GOT_CORE_FOUNDATION = 1;
This functionality probably won't bring any major new benefits yet, though it similarly shouldn't break things when enabled. Once I get it polished up a little more, I'll turn my attention to contributing some code that takes advantage of the new functionality.
As always, comments and suggestions are welcome. Bill