ptpd: new package

Add the new ptpd package, loosely based on the one from bug #2305.
This one handles the IEEE 1588-2002 spec.

[Peter: mark init script as executable]
Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>