I've been told shadows are "easy", so add all the bindings and state management for them, so if someone were to feel like implementing them, they could just do the graphics.

Meanwhile, add some missing exception-raising checks, fix some bugs in color parsing, and implement the missing isPointInPath with Fredrik's help.

(Also fix the licenses BSD->LGPL in html/html_canvasimpl.*, since I merged code over from LGPLd ecma/kjs_context2d.*. I suck for not noticing this sooner and presuming the two would be the same, coming in at the same time)