[$] Shedding old architectures and compilers in the kernel

The kernel development process tends to be focused on addition: each newrelease supports more drivers, more features, and often new processorarchitectures. As a result, almost every kernel release has been larger than itspredecessor. But occasionally even the kernel needs to slim down a bit.Upcoming kernel releases are likely to see the removal of support for anumber of unloved architectures and, in an unrelated move, the removal ofsupport for some older compilers.