Add missing pins 3 and 5

https://www.xppower.com/portals/0/pdfs/SF_ITX.pdf

When reviewing https://github.com/KiCad/kicad-footprints/pull/2079, I noticed that one of the symbols was missing pins 3 and 5. And the footprint has those pins so we need them. I think the others are OK but maybe my eyes are bleary.

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All contributions to the kicad library must follow the KiCad library convention

Thanks for creating a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items:

• Provide a URL to a datasheet for the symbol(s) you are contributing
• An example screenshot image is very helpful
• Ensure that the associated footprints match the official footprint library
  • A new fitting footprint must be submitted if the library does not yet contain one.
• If there are matching footprint PRs, provide link(s) as appropriate
• Check the output of the Travis automated check scripts - fix any errors as required
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