[New feature] Check for incoming leap second

- Add a new tool (wrs_leapsec) to check for an incoming leap second. It
is done by parsing the leap second file. If a leap second is detected
then adjustment parameters for the clock algoritm are set in the kernel.
- Start the tool at startup
- With cron, execute the tool every 3 hours
- As many tools need to parse the leap seconds file, functions have been
added in the library and then called by these tools