Support for multiple memory segments.

I'm working on multiple memory cache support which has been on my  
todo for a long time now (used for different cache behavior, testing,  
lock performance, smaller coredumps with meaningful information, and  
larger user caches).

Do we still need to support the multiple segments to work around  
system memory limitations with traditional shared memory segments?  I  
believe everyone can use mmap now to get around this, but perhaps  
there's some system out there that I'm not aware of that requires this??

If we don't need it I'll drop support in my patch as multiple-within- 
multiple-segments is a bit much ;-)

Thanks,

-shire