RevBy:  con

make "Hello World" plugin compilabe

Details:
Still not perfect due to inverted gradients, but much better.

RevBy:    trust me
Details:
Now that hover is correctly implemented for
toolbuttons, we actually have to check the sunken
state.

Details:
This ensures that the manhattan button arrow does not depend on the
menubutton indicator size, which it should not.

Scrolling is broken for plain QTextEdit.