Add initial video playback support for Ogg Theora videos (resolves issue #66.)

The basic APIs are:

video = love.graphics.newVideo("myvideo.ogv")

love.graphics.draw(video, ...) -- Video objects are Drawables.

video:play(), video:pause()

video:getDuration(), video:tell(), video:rewind(), video:seek(seconds)

video:getSource()

video:getWidth(), video:getHeight(), video:setFilter(min, mag)

More advanced APIs include video:setSource(source), video:getStream(), and videostream:setSync.

To use a custom pixel shader when drawing a Video, call the new TexelVideo(texcoords) function instead of Texel(texture, texcoords) in order to get the pixel colors of a video frame.

src/common/Object.h

@@ -117,6 +117,16 @@ public:
 		return object;
 	}
 
+	operator bool() const
+	{
+		return object != nullptr;
+	}
+
+	operator T*() const
+	{
+		return object;
+	}
+
 	void set(T *obj)
 	{
 		if (obj) obj->retain();