added PopoverViewCompatibility.h

Adds compatibility to compile under 6.x without warnings, e.g. fixes:  

![screen shot 2013-07-22 at 6 58 45 am](https://f.cloud.github.com/assets/404757/834625/1b4375c0-f2c6-11e2-9a61-a89120eaebf0.png)