[FS#470] Add ipt-netflow as a package in standard distribution

[LEDE Bugs]

The following task has a new comment added:

FS#470 - Add ipt-netflow as a package in standard distribution
User who did this - Felix Fietkau (nbd)

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It should be submitted to https://github.com/openwrt/packages instead
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=470#comment1822