Upgrade FBAudienceNetwork to 3.18
Merge pull request #91 from wuzhiming/plugin_fb_5th

Feature #5950: add Facebook SDK change some feature
Merge pull request #92 from pandamicro/develop

Upgrade FBAudienceNetwork to 3.18
Merge branch 'develop' of https://github.com/cocos2d-x/plugin-x into v3_facebook_update