This is a minimal ripping of headers out of the kernel source tree and
contains only what is needed in order to install headers for an architecture.

See the rip-headers.sh script for exact details on what files were copied.

Self links:

* https://wiki.gentoo.org/wiki/Project:Toolchain/sys-kernel/linux-headers
* https://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo/src/patchsets/gentoo-headers/
