'syswait' command added to be used in system libraries

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
mill_select and mill_syswait separated

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

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>
handler prologue simplified a bit

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