[syslog-ng] [PATCH (3.4) 0/1]: value-pairs: Add value_pairs_foreach_sorted().

[Gergely Nagy]

The patch that will follow shortly implements a
value_pairs_foreach_sorted() function, that can be used for multiple
purposes in the future:

- Template functions that want to format their output with keys always
  in a predictable order.
- Various other parts of the code, that work better when operating on
  a sorted collection.

I'm submitting it separately, so that it'll be easier for me to build
upon it in the not too distant future.

(And because I almost forgot to send it, even though it was origianlly
made in early november...)