[exim] NO_POLL_H

What is this line in os.h-Darwin do? Does it strip the code from
spam.c or just allows building binaries without pulling up an error?

#define NO_POLL_H

Either case, scanning for spamassassin is problematic unless poll()
function is stripped. (to the way it was in 4.51)

Has anybody replaced poll with select and succeeded in building for OSX?