I've searched everywhere for an example of the statement needed in the theme.info file so that the theme can store Panels 3 layouts. I've tried both:
plugins[panels][plugins] = layouts
plugins[panels][layouts] = layouts
...and put my custom panels layouts into layouts/test inside my theme, where test is the name of my panel layout, and contains test.inc, test.css and test.png.
However it refuses to work. Can someone enlighten me?