[$] Atomic kmaps become local

The kmap() interface in the kernel is a bit of a strange beast.It only exists to overcome the virtual addressing limitations of 32-bitCPUs, but it affects code across the kernel and has side effects on 64-bitmachines as well. A recent discussion on the handling of preemption withinthe kernel identified a number of problems in need of attention, one of which was the kmap()API. Now, an extension to this API called kmap_local() isbeing proposed to address some of the problems; it signals another step inthe kernel community's slow move away from supporting 32-bit machines asfirst-class citizens.