Unbreak master page rendering in ODPs.

Restricted the `z-index: 1` hack for `draw|frame` to frames within `office|text` since it was only intended for ODTs in the first place.

This restores the master pages' content behind the body pages' as it should be. ODPs look better like before now.

[This](http://www.kde.org/kdeslides/CampKDE2010/CampKDE2010-CelesteLynPaul.odp), before and after the fix:

![before](https://cloud.githubusercontent.com/assets/591038/2666651/63e1e5b0-c0a1-11e3-9347-93d3832dae6c.png)
![after](https://cloud.githubusercontent.com/assets/591038/2666650/63ddda06-c0a1-11e3-872d-f9c8d68fc7b0.png)