Restore dup of interruptfd

Merge branch 'non_invasive' of https://github.com/dallison/co into no…

…n_invasive

Fix POLL build

Add changes for Cruise

Build with older GCC

Fix event trigger on mac os

Init poll interrupt fd to -1

Add docs for new features

Merge branch 'main' of https://github.com/dallison/co

Merge pull request #16 from dallison/multifd

Allow multiple fds on epoll