Fix strokeRect to check the given width.

The state strokeWidth isn't used, so don't check for it to be 0.
Translate graphic constext using transforms.

Now that the app_server bug is fixed, this works fine.
Completely switch to picture-based clipping.

Region-based clipping always work in the view coordinate space, and is
not affected by the view transform. This is by design: there would be no
way to transform a region while keeping it implementes as a set of
BRects all while keeping a fast intersection test.

Use Picture clipping which can work the way we need even when transforms
are involved. This fixes several drawing and clipping problems, but the
current implementation is rather slow, using a lot of CPU on app_server
side.