added DEBUG_GL_ERROR debug functionality

git-svn-id: svn://anubis/anaglym/trunk@188 99a6e188-d820-4881-8870-2d33a10e2619

tests/bowling.lua

@@ -57,6 +57,7 @@ end
 function update_overlay_event(width, height)
     local tw, th = ag.getTextSize("Hi there", 18)
     ag.drawText("Hi there", 1, 1, 0, 18, width - tw - 40, height - th - 40)
+    ag.drawText("Hello", 1, 0, 1, 20, 200, 200)
 --    ag.drawLine(1, 0, 0.3, 10, 10, 40, 60)
 --    ag.drawLine(1, 0.7, 1, 50, 10, 100, 60, 5)
 --    ag.drawRect(0, 1, 0, 40, 40, width / 2, height / 2)