Don't call InvertPixelArray with negative width and/or height.
For buffered icon draw do some clipping to avoid bad thinks
happening while code is trying to draw outside of bitmap (caused
by bad calculations for text length where TextLength() is not good
enough and should be repalced with TextExtent()).
Don't redraw all icons while scrolling.
Fixed some do not render if not necessary things in DrawIcon() which
after introduced buffering were no longer working or no longer working
correctly.
git-svn-id: https://svn.aros.org:8080/svn/aros/trunk/AROS@25391 fb15a70f-31f2-0310-bbcc-cdcc74a49acc