minor #201 [UUID] speedup implementation (lyrixx)
minor #201 [UUID] speedup implementation (lyrixx)

This PR was merged into the 1.13-dev branch.

Discussion
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[UUID] speedup implementation

```
>…github.com/lyrixx/symfony-polyfill(master) php test.php
[Symfony][v4] 4.835s
>…github.com/lyrixx/symfony-polyfill(uuid) php test.php
[Symfony][v4] 1.558s
```

Commits
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c928909 [UUID] speedup implementation

nicolas-grekas/polyfill,symfony/polyfill