Use automatic batching for love.graphics.print/printf.

This doesn’t actually improve performance at all in most cases, but it does remove some OpenGL-specific code from the Font files, and reduces the amount of duplicated rendering code. This makes it slightly easier to add support for Core Profile OpenGL 3.

--HG--
branch : minor

src/modules/graphics/opengl/Text.h

@@ -86,6 +86,7 @@ private:
 
 	StrongRef<Font> font;
 	GLBuffer *vbo;
+	QuadIndices quadIndices;
 
 	std::vector<Font::DrawCommand> draw_commands;