Added frr-gentoo overlay

[f0o]

No description provided.

[ChrisADR]

Hi @f0o, please review these points:

• You need to copy/paste the GITHUB TEMPLATE (located in files/overlays/repositories.xml)
• The list is Name sorted, which means that your XML input needs to be on the 'F' segment, not the end of the list.
• Please rebase all your fixes in a single commit with the appropriate name (Added frr-gentoo overlay); if you don't know how it would be easier to create a new PR when all is fixed.

Thank you

[mgorny]

What @ChrisADR said.

[f0o]

@ChrisADR Will do tomorrow, there's also a chance that the source-location of the overlay may change if FRR decides to take over. So there's no rush from my side right now.

I'm closing and re-opening a new PR so your team wont have dangling, stale, PRs in the queue.