Split general WT_BTREE fields into WT_DATA_HANDLE.
Rename {conn,session}_btree.c to {conn,session}_dhandle.c.

--HG--
rename : src/conn/conn_btree.c => src/conn/conn_dhandle.c
rename : src/session/session_btree.c => src/session/session_dhandle.c
Replace session->btree with a data handle.
Merge branch 'develop' into data-handles

Conflicts:
	src/btree/rec_write.c
	src/conn/conn_dhandle.c
	src/cursor/cur_index.c
	src/schema/schema_drop.c
Merge branch 'develop' into data-handles

Conflicts:
	src/btree/bt_handle.c
	src/conn/conn_dhandle.c
	src/cursor/cur_file.c
	src/include/btree.h
	src/include/cache.i
	src/include/extern.h
	src/lsm/lsm_worker.c
	src/session/session_dhandle.c
	src/support/hazard.c
Merge branch 'develop' into data-handles

Conflicts:
	src/btree/bt_evict.c
Flush LSM chunks before checkpointing: the checkpoint requires the schema lock (among others), and we want to hold that for as short a time as possible.
Add a condition variable to signal when LSM checkpoints should start, rather than sleeping for a fixed amount of time.  While in this code, cleanup places that set session->btree in order to make a function call.
Change LSM drops in the background to avoid blocking application threads.
Move the LSM "switch" operation into the worker thread.  This should both reduce contention for the schema lock and allow application threads to keep working until the new file is ready.
Use adaptive mutexes for spinlocks if available.
Merge branch 'develop' into data-handles

Conflicts:
	dist/filelist
	src/block/block_mgr.c
	src/btree/bt_cell.c
	src/btree/bt_curnext.c
	src/btree/bt_curprev.c
	src/btree/bt_debug.c
	src/btree/bt_evict.c
	src/btree/bt_handle.c
	src/btree/bt_slvg.c
	src/btree/bt_stat.c
	src/btree/bt_vrfy.c
	src/btree/bt_vrfy_dsk.c
	src/btree/rec_write.c
	src/btree/row_srch.c
	src/conn/conn_dhandle.c
	src/cursor/cur_file.c
	src/cursor/cur_index.c
	src/cursor/cur_stat.c
	src/include/api.h
	src/include/btree.h
	src/include/btree.i
	src/include/cache.i
	src/include/extern.h
	src/include/serial.i
	src/include/stat.h
	src/include/wt_internal.h
	src/lsm/lsm_cursor.c
	src/lsm/lsm_worker.c
	src/meta/meta_track.c
	src/schema/schema_drop.c
	src/schema/schema_plan.c
	src/schema/schema_truncate.c
	src/session/session_api.c
	src/session/session_dhandle.c
	src/txn/txn_ckpt.c
Merge branch 'basho' into lsm-ckpt-experiments
Merge branch 'develop' into data-handles

Conflicts:
	src/btree/bt_evict.c
	src/btree/bt_handle.c
	src/btree/bt_page.c
	src/btree/rec_evict.c
	src/conn/conn_dhandle.c
	src/cursor/cur_stat.c
	src/include/btree.h
	src/include/btree.i
	src/include/stat.h
	src/lsm/lsm_cursor.c
	src/schema/schema_create.c
	src/txn/txn_ckpt.c
Merge branch 'develop' into data-handles
Update new code to use data handles.
Merge branch 'develop' into data-handles
Merge branch 'basho' into lsm-ckpt-experiments

Conflicts:
	src/include/wiredtiger.in
Minor fixes for data handles: fix loop termination in eviction, remove obsolete files, cleanups for s_all.
Track cursor creation in the statistics (as demonstrated by the Basho
benchmarks, creating a cursor per operation isn't a good idea).