worker tasks use src constants (POSIX version)

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
worker_task uses src constants (win version)

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
worker_op uses src constants (win version)

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>