Remove support for extended (non-PC) x86 platforms

None of these platforms were enabled anyway
Always use David's latest integration branch

This removes the "integration" option and changes the default git
repository to github.com/kdave.
Simplify getting FILES value for parent repository

It turned out to be quite easy, if very unintuitive.
Remove paranoid FIXME

It's a silly proprietary licence anyway, who knows how strange and
particular it is.