Init a new Timespec from now.

Property definitions

realtime $ Timespec :: monotonic_now
	# Init a new Timespec from now.
	new monotonic_now `{
		struct timespec* tv = malloc( sizeof(struct timespec) );
		nit_clock_gettime( CLOCK_MONOTONIC, tv );
		return tv;
	`}
lib/realtime/realtime.nit:68,2--73,3