[GSoC] Initial numbers on xlsx load time

[Markus Mohrhard]

Hey Daniel,

> Hi Kohei,
>
> I'm glad to hear our efforts are making a difference.  Let's see if we can
> keep knocking seconds off those load times.  :-)
>

I've finally spend some time reviewing your patches and merged them
into master. I just squashed the tab cleaning patches into the
relevant commits before pushing to master. I also added this great
improvement to the 3.6 Release Notes at
http://wiki.documentfoundation.org/ReleaseNotes/3.6

Keep up this great work.

Regards,
Markus