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.
If a session already has a reference to a dhandle, don't add another.
Merge Sue's fix for the session refcount with mine, simplify.
Merge pull request #811 from wiredtiger/huge-kv

huge key/value support.
Fix some 64-to-32-bit conversion warnings on OS X.

refs #811
Merge pull request #812 from wiredtiger/session-ref

If a session already has a reference to a dhandle, don't add another.
../src/block/block_write.c: In function '__wt_block_write_off':
../src/block/block_write.c:190:6: warning: conversion to 'long unsigned int' from 'int64_t' may change the sign of the result [-Wsign-conversion]
../src/block/block_write.c:190:29: warning: conversion to 'int64_t' from 'long unsigned int' may change the sign of the result [-Wsign-conversion]

refs #811