参考地址:http://forum.unity3d.com/threads/error-unknown-type-name-__declspec-after-xcode-7-3-upgrade.393128/
http://stackoverflow.com/questions/35192700/how-to-get-rid-of-unknown-type-name-declspec-error-in-xcode
我用的unity版本时5.3.1f1,最简单直接的方法是升级unity到最新版本。
Unity just released a new version, 5.3.2, to deal with this issue.