[REVIEW 3-6] Performance improvement for large pivot table cache

Hi there,

I'd like to have the following commit

http://cgit.freedesktop.org/libreoffice/core/commit/?id=1e3d97dfe9747fa70cdcf642a4a710c3d90cc95c

cherry-picked to 3-6.  The change may look non-trivial, but all it
does is to expose the internal API and set two boolean flags directly
instead of going through the UNO layer, which happens to be very very
expensive for this particular scenario.  This speeds up the import of
xlsx documents with large pivot cache from upwards of 10 minutes down
to just 10 seconds.  Unfortunately the test document I used is
confidential, so I can't share it publicly.

Review and cherry-pick appreciated.

Kohei