Blender Git Loki

Various tweaks to View2D code for handling of scrollbar interactions in relation to bug 19881:

* Clearly labelled the way that the scrollbar hiding works. Also see the report comments for an overview
* Added another pair of flags for another one of the cases in which scrollbars should also get ignored; when the entire contents of the view are visible, a pair of flags is now set in the view2d data (instead of for the scrollers tempdata only) for detecting this case too
* Fixed the potential for scrollbars without zoom handles shown to have those handles still considered. This still happened in the User Preferences window, but has now been disabled.

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These changes still don't solve the bug though. Currently after the scrollbar operator passes through, the Outliner's activate-selection operators still fail to start.