Large memory support

[Jason Titus]

Looks like we just stumbled onto some 32 bit limits in memcached.  Just =
wondering how you guys want to deal with supporting >2GB per cache.  We =
have experimented with switching some of the unsigned ints into unsigned =
long longs and it seemed to work (>4GB seemed ok.  No thorough testing =
yet though).  A cleaner solution might be adjusting the memory related =
variables to size_t or some such so that they work well on 32 and 64 bit =
systems.

What makes the most sense to you folks?

Jason