Fix typo. Thanks diger for noticing!
Fix include path again

AffineTransform.h in WebKit conflicts with our version. It is now
included by View.h, so make sure WebKit one isn't in the system include
path.
Enable and use the ClipToPicture-based clipping.

* Fixes the issues with the sidebar on www.haiku-os.org.
* Does not fix dev.haiku-os.org; haikuports.org, and others, yet.

I had to change the text drawing code to do a complete
PushState/PopState instead of saving only the color and drawing mode. I
have no idea why this is needed. If I don't do this, sometimes the text
isn't drawn at all.