uses ccGLBlendFunc instead of glBlendFunc

so that Cocos2dx automatically preserve and switch back to old OpenGL mode
See ccConfig.h line 50

spine-cocos2dx/src/spine-cocos2dx/CCSkeleton.cpp

@@ -67,7 +67,7 @@ void CCSkeleton::update (float deltaTime) {
 
 void CCSkeleton::draw () {
 	CC_NODE_DRAW_SETUP();
-	glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+	ccGLBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
 	skeleton->draw();
 
 	if (debug) {