* KASM-5417 fix bug watermrk multi-display
* Force the zlib expected size to an int, it was unexpectedly float
* KASM-5427 transparent rects not drawn on primary display
* add double buffer when transparent rects are used
* refactor of transparent rects
* Use a more descriptive zlib error
* account for dropped transparent rects
* fix bug with multi-monitor with overlay