Add ProtocolUser for custom system plugins.
issue #2305:remove unneeded comment
Merge branch 'develop' into ForUser

Conflicts:
	plugin/protocols/platform/android/PluginFactory.cpp
	plugin/protocols/proj.android/jni/Android.mk
Merge branch 'develop' into ForUser
issue #2317, Adjust ProtocolUser for actual situation.
issue #2317, Add plugin qh360 .
closed #2317, Add sample project HelloUser.
Merge branch 'develop' into ForUser
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into develop
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into develop
Modify the min sdk version of android platform required in plugin samples.
Modify the target version of plugin samples to android-10.
issue #2305: Using std::thread instead of pthread for ScriptingCore.
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into iss2305-replace-pthread
issue #2305:use c++11 thread correctly
issue #2305: sched_yield(); --> std::this_thread::yield();
closed #2305: fix a running time error
Merge pull request #3005 from dumganhar/iss2305-std-thread

issue #2305: Using std::thread instead of pthread for ScriptingCore.
Merge pull request #3006 from minggo/iss2305-replace-pthread

fix some errors of c++11 thread usage in CCTextureCache
Merge pull request #3000 from natural-law/develop

Add ProtocolUser for user system.