Fixed siridb_time_now returns incorrect number in arm32 build

[srdgame]

We had siridb-server in our ARM device which Cortex-A7, and the siridb_time_now returns incorrect number.

if time.tv_sec is 1614844851 and time.tv_nsec is 490840489, with factor 1000, the siridb_time_now returns 4232115490.

The ARM device is running OpenWRT with musl

[joente]

@srdgame , I think we may just as well just use uint64_t for the factor property. That will most likely also solve the arm32 build problem. See #170

[srdgame]

@joente OK, I will close this