Don't abuse PRNG -> fix identifier generation when building on Windows

[hillu]

Pseudorandom number generators need to be initialized only once.

Using the system time for this is Generally Fine, but re-initializing the PRNG in a tight loop every time a random number is needed significantly raises the odds that the same number sequence (or even the same number) is returned every time.

Chances for this to happen on Windows are apparently much higher than on Linux. Not sure why this is the case, my best guess is that the clock used for Go's `time.Now()´ runs with coarser granularity.

[hillu]

@Tylous Is this PR at all interesting to you?

[Tylous]

This is needed for it to work on Windows as well as Linux and and OSX