Finish migration to cmake

[crazyhappygame]

@minggo
Created based on discussion https://discuss.cocos2d-x.org/t/v4-would-be-a-good-time-to-move-things-forward/47962/44?u=crazyhappygame

To-do
https://github.com/cocos2d/cocos2d-x-external/blob/master/src/CMakeLists.txt

• # add_subdirectory(curl)
• # add_subdirectory(glfw)
• # add_subdirectory(luajit)
• # add_subdirectory(websockets)

[minggo]

@crazyhappygame thanks.

[crazyhappygame]

@PatriceJiang I propose to work on this in following order luajit, websockets, glfw, curl.

[crazyhappygame]

@PatriceJiang

1. I invested lots of time into this project (please check commit history) but I am not sure if anyone else is interested in that.

2. When we will finish with those few libraries ( luajit, websockets, glfw, curl) after that we have to replace current cocos2dx prebuilds with this repo. Does cocos2dx team will accept this change?