Backed out changeset 21e52e54ea4d
Merge branch 'develop' into fast-checkpoints
Re-enable fast checkpoints.
Merge branch 'develop' into fast-checkpoints
Merge branch 'develop' into fast-checkpoints
Merge branch 'develop' into fast-checkpoints
Merge branch 'develop' into fast-checkpoints
Change the block manager to not touch the WT_ITEM.{mem,memsize} fields
when mapping object into memory, remove the WT_ITEM_MAPPED flag, that
information is now based on WT_DATA_IN_ITEM (if the WT_ITEM.data field
points into the WT_ITEM.mem buffer).  This also simplifies some of the
buffer handling, there's no longer any reason to "clear" WT_ITEM.mem
for mapped objects.

Some calls to __wt_buf_steal() used scratch buffers, which is dangerous,
scratch buffers can include large allocated chunks; remove/replace all
calls to __wt_buf_steal() with __wt_strndup() calls.
Prefer real pointer types over void * when there is no ambiguity.

refs #974
Merge pull request #974 from wiredtiger/map-item-cleanup

WT_ITEM cleanup
Merge branch 'develop' into fast-checkpoints
Don't try to "help" checkpoints from eviction threads: we can't get the snapshot right, so this was only ever approximate, and the checkpoint has just written all the dirty pages as part of the "write leaves" step, so if we can't find clean pages, it's unlikely we'll be able to write them correctly.  Remove the WT_SKIP_UPDATE_OK flag: it is no longer needed.

refs #963
Merge pull request #963 from wiredtiger/fast-checkpoints

Fix fast checkpoints