Ensure that the WT_CURSOR::uri field matches open_cursor URI.

Since we document that is how it works.
Fix which URI is used by schema truncate.
Return error from cursor open.
Remove lsm=(merge_threads) configuration option.

It's been replaced by lsm_manager=(worker_thread_max). Update
all places it was used in our tree, and add note to upgrade doc.
Merge branch 'develop' into cursor-uri-protect
Trivial simplification, we don't need a local variable.
Don't ignore error return from WT_CURSOR.close (it might be a panic).
Merge pull request #1235 from wiredtiger/cursor-uri-protect

Cursor uri protect
Don't drop core if we fail to allocate the WT_BLOOM structure (jump to
error lable will indirect through bloom).
Leave the returned bloom structure reference set to NULL on error.
When opening simple tables, the table code calls the cursor open
function recursively (on the underlying data source), in which case the
application's URI has already been copied, don't copy it again and leak
the memory. Reference #1234, #1235.
Make text match example.
Merge pull request #1238 from wiredtiger/remove-merge-threads

Remove lsm=(merge_threads) configuration option.