WL#2616: Support for interleaved CREATE TABLE ... IF NOT EXIST

Affects: Server-7.1   —   Status: Un-Assigned   —   Priority: Medium

If an application is performing interleaved CREATE TABLE ... IF NOT EXIST
on several MySQL servers the effect should be that both succeeds.
If handler discovers that table already has been created, we should
check if the .frm's are identical and return success to the caller
if that is the case.