clock: tick: added the sys tick to the irq subsys

The system tick for AVR is now handled by the IRQ subsystem. On system
initialisation the the AVR subsystem requests an IRQ (using irq_request)
for the AVR TIMER0 overflow interrupt. This interrupt is fired every
milisecond and registers this tick in a 64 bit atomic integer.

Signed-off-by: Michel Megens <dev@michelmegens.net>
libc: printf: updated printf for long ints.

vfprintf is from now on also able to handle long and long long int (and
its unsigned counter parts).

Signed-off-by: Michel Megens <dev@michelmegens.net>