Rename Framebuffer to Canvas (issue #263). Move error reporting code.

Error reporting now resides in Graphics::newCanvas() instead of the
previous location wrap_newFramebuffer(). Changed error text for
"Error in implementation" to point to a possible fix.

src/modules/graphics/opengl/wrap_Canvas.h

@@ -0,0 +1,29 @@
+#ifndef LOVE_GRAPHICS_OPENGL_WRAP_CANVAS_H
+#define LOVE_GRAPHICS_OPENGL_WRAP_CANVAS_H
+
+// LOVE
+#include <common/runtime.h>
+#include "Canvas.h"
+
+namespace love
+{
+namespace graphics
+{
+namespace opengl
+{
+	//see Canvas.h
+	Canvas * luax_checkcanvas(lua_State * L, int idx);
+	int w_Canvas_renderTo(lua_State * L);
+	int w_Canvas_getImageData(lua_State * L);
+	int w_Canvas_setFilter(lua_State * L);
+	int w_Canvas_getFilter(lua_State * L);
+	int w_Canvas_setWrap(lua_State * L);
+	int w_Canvas_getWrap(lua_State * L);
+	int w_Canvas_clear(lua_State * L);
+	int luaopen_canvas(lua_State * L);
+
+} // opengl
+} // graphics
+} // love
+
+#endif // LOVE_GRAPHICS_OPENGL_WRAP_CANVAS_H