rpcrt4(2/2): Use pseudo-random numbers to generate UUIDs rather than using the (old, deprecated) MAC-address-and-time generation algorithm

[Juan Lang]

> The change is OK but you'll want to flesh out RtlGenRandom first,
> currently it will fail pretty badly if /dev/urandom isn't available.

Ah, good point.  Thanks.  Where isn't it available, out of curiosity?
--Juan