Discard the error message when there aren't any files.
Make the async methods follow the same grouping conventions as
cursor/session: compact == table operation, search == cursor
positioning.
Return EBUSY if no async handles available and fix ex_async to look for it. #1153.
Use ::XXX to link to global types, make WT_ASYNC_OPTYPE links
work.
WT_ASYNC_OP.{id,get} don't return errors.
Fix doc to use correct method names get_id and get_type.
Don't describe the WT_ASYNC_OPTYPE operations inline, point to the
method they represent instead (insert isn't always an "insert", so
don't even try).
Document EBUSY and update python. #1153
Switch WT_CONNECTION.async_new_op calls to use EBUSY; reference #1153.
Replace goto's around async_new_op calls with a simpler while loop.
Minor wordsmithing.
Don't write method wording for the WT_ASYNC_OP methods, instead point
to the underlying WT_CURSOR/WT_SESSION wording.
Clarify return values sent via the callback.