SVN commit 799411 by mart:

use a separate cache for each elementPrefix, this will speed up
rendering a lot if prefixes are switched very often. this will make
possible for instance to render the background of taskbar items with a
PanelSvg.
This behaviour is disabled by default, you can enable/disable it with
setCacheAllRenderedPanels(bool), get with cacheAllRenderedPanels() and
erase the entire cache with clearCache()


 M  +176 -114  panelsvg.cpp  
 M  +18 -0     panelsvg.h