Coding guideline: Added editorconfig

Feel free to use editorconfig together with the according
emacs/vi/sublime plugin.

Silently removed old gen_build_env.

Put /usr/include to cppcheck include paths, as we
are actually using these headers in i386..
(Should we really do that?!)

Change-Id: I31666c088f2d1a6c0f2f3a99af1af35d52d2767f