Patch to fix the build issue on MacOS 10.9.4

[Poul-Henning Kamp]

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In message <CEC21A4E-AE8C-4716-ABE5-D54D18117E99 at gmail.com>, Meng Zhang writes:

>Here ( https://github.com/varnish/Varnish-Cache/pull/46 ) is a =
>pull-request to fix the build issue on MacOS 10.9.4.

I've fixed it slightly differently to avoid the unreadability of PRIu64 and friends.

Let me know if there is anything else...

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