Installed via board manager URL.
Somehow I get lost of the files of the staging release and the preferences.txt
I modified the preferences.txt again. Made a download of the staging release, and imported again all needed libs (e.g. streaming.h).
Now I am not able to compile my project any more. It worked before the crash!
First problem is, that the compiler doesn't find the stdlibs.h any more. It is called from streaming.h.
No idea why. Arduino IDE is the same, and the staging is also the same?
ESP8266 Arduino add-on
Arduino IDE 1.6.5