Getting multiarch upstream

Konstantinos, Loïc, and I talked last night about multiarch. Linaro want multiarch and will use it in all our products and hence need to get it upstream. There's another meeting in a week to figure out what's next.

I've written a page on the uses, issues, and history at: https://wiki.linaro.org/MichaelHope/Sandbox/MultiarchNotes

Please edit and add and correct things. The page isn't Linaro's position but we need to have answers for the arguments.

I see no particular blockers especially if we separate the concerns.

-- Michael