InnoDB Plugin locks table

This is a pre fix update that does the change to the handler api.

This is done since there are already changes in this version,
so the real fix does not need to change the api.

sql/handler.h:
  Bug#37453: Dropping/creating index on partitioned table with
  InnoDB Plugin locks table
  
  The check for which alter table flags a handler have is done through the
  handlerton, which will not work correctly for any partitioned table.
  It must be through the handler interface.
  
  To be able to fix this I have to add a virtual function to the handler class.