Fix portability issues. Add poll.h to header checks.
Fix portability issues. Add poll.h to header checks.

doctaweeks/umurmur,snowblind/umurmur,doctaweeks/umurmur,fmorgner/umurmur,troxor/umurmur,fmorgner/umurmur,doctaweeks/umurmur,snowblind/umurmur,troxor/umurmur