Clustered APIC setup patch.  Needed to support generic systems with more
than 8 CPUs.

Motivation:

 The current APIC destination mode ("Flat Logical") used in linux kernel
 has an upper limit of 8 CPUs.  For more than 8 CPUs, either "Clustered
 Logical" or "Physical" mode has to be used.

 The attached patch adds support such systems by organizing them into
 logical clusters, with each cluster having 4 CPUs.  This is activated by
 a new config option "Support for other sub-arch SMP systems with more
 than 8 CPUs", under Processor feature->Sub architecture.

 The patch is made very simple and isolated, thanks to Martin J.
 Bligh's patchsets, which has moved all APIC related functions into
 sub-arch macros.  Has zero impact on standard systems.

 This patch enables all 16 logical processors on a generic, non-quad
 based, system that we have here.  Also, by looking at SuSE source, I
 have also added a special switch, to specifically support Unisys
 (ES7000).  Just replacing #define SEQUENTIAL_APICID by CLUSTERED_APICID
 in the patch should make it work on ES7000(not tested).