InnoDB Plugin locks table

The fast/on-line add/drop index handler calls was not implemented
whithin the partitioning.

This implements it in the partitioning handler.

Since this is only used by the not included InnoDB plugin, there
is no test case. (Have tested it manually with the plugin, and
it does not allow unique indexes not including partitioning
function, or removal of pk, which in innodb generates a new pk,
which is not in the partitioning function.)

NOTE: This introduces a new handler method, and because of that
changes the storage engine api. (One cannot use a handlerton to
see the capabilities of a table's handler if it is partitioned.
So I added a wrapper function in the handler that defaults to
the handlerton function, which the partitioning handler overrides.