Don't count applications where no compression is configured as instances
of the buffer being too small to compress.
Better/fixed support for huge keys/values.

Change the WT_ITEM::size field from type uint32_t to size_t.

Change test/format configuration to support large key/value items.

Ref: #808 and #70.
Merge pull request #811 from wiredtiger/huge-kv

huge key/value support.