reconsider signature of rcl_clock_get_now

[dirk-thomas]

Currently the function takes a rcl_time_point_t * but neither checks the clock_type nor set the clock_type:

rcl/rcl/src/rcl/time.c

Lines 228 to 240 in d3a734f

	rcl_ret_t
	rcl_clock_get_now(rcl_clock_t * clock, rcl_time_point_t * time_point)
	{
	RCL_CHECK_ARGUMENT_FOR_NULL(time_point, RCL_RET_INVALID_ARGUMENT, rcl_get_default_allocator());
	if (clock->type && clock->get_now) {
	return clock->get_now(clock->data,
	&(time_point->nanoseconds));
	}
	RCL_SET_ERROR_MSG(
	"clock is not initialized or does not have get_now registered.",
	rcl_get_default_allocator());
	return RCL_RET_ERROR;
	}

Should the signature be changed to a rcl_time_point_value_t instead?

[dirk-thomas]

See proposed changed (part of #272): 28e6ba1