Don't attempt to split pages when checkpoints are active in a tree.

refs #1419, SERVER-16336
Only do in-memory splits on large, dirty pages.
Don't try in-memory splits when closing a tree.
Merge pull request #1427 from wiredtiger/split-fixes

Fixes for in-memory splits
Reduce the chunk size in evict-lsm wtperf workload.

We aren't trying to stress out what happens when the cache gets full.
Changes in #1204, #1288 mistakenly changed the values for some error
defines, which breaks backward compatibility. (The WT_DEADLOCK error
name sorted differently from WT_ROLLBACK, and we were assigning error
values based on the sort order in a script.) Revert the change, and make
sure it doesn't happen again.
Use the new WT_LSM_TREE_SWITCH_INPROGRESS flag to push work units
instead of using the switch_txn setting as that is now set much later.
Merge pull request #1430 from wiredtiger/revert-error-value-change

Revert error return value changes.
Merge pull request #1432 from wiredtiger/lsm-switch

Create WT_LSM_TREE_SWITCH_INPROGRESS flag
Change the Python scripts to follow Python indenting standards (4 space
indents, spaces only).
Fix the error messages
Merge pull request #1433 from wiredtiger/python-style

Reformat all Python files to use 4-space indents
Merge branch 'develop' into evict-rename