Make the qpic_t struct consistent with the internal layout.

Now that the renderer ruamoko builtins use handles, there's no need to
hide data, and it's safer anyway.

ruamoko/include/draw.h

@@ -6,6 +6,7 @@
 struct _qpic_t {
 	int width;
 	int height;
+	int handle;
 };
 typedef struct _qpic_t *qpic_t;