[Libreoffice] [REVIEW]patch improving calc file loading time

[Laurent Godard]

Hi all

could you please have a look at this patch

it avoids multiple calls to maTables.back() that waste time on loading a
calc file. the idea is to store the last table needed and use this
instead of retreiving it each time from maTables

on a pathological calc file this drastically improve the loading time
(near 35% in certains cases)

this patch is based on 3.4 branch and targets the 3.4.4 at least

thanks again to markus for his great mentoring

Laurent