center moves on undo and duplicate after skew and rotation

[KoRi]

In .46, still in rev. 20525

After transforming objects with center moved from default position in one of the following ways:

- rotate 90deg using the icons on the 'Tools controls bar'
- rotate using the transform dialog with 'Apply to each object separately' set
- skew using the transform dialog with 'Apply to each object separately' set

Undoing the rotate/skew or rotated/skewed object duplicating the object causes the center to move while it should stay in place.

I could track down the cause to be the functions sp_item_rotate_rel() and sp_item_skew_rel() in sp-item-transform.cpp not updating the XML representation ie. not calling updateRepr() of the objects after changing the center position.

The attached patch solves the problem :-)

[bbyak (buliabyak)]

thanks, patch committed, please keep contributing! :)