New formula: clang-complete

clang-complete is Executable in [emacs-clang-complete-async](https://github.com/Golevka/emacs-clang-complete-async).

emacs-clang-complete-async is an emacs extension to complete C and C++
code, it uses libclang to parse the source code on the fly and provides
completion candidates to [auto-complete](https://github.com/auto-complete/auto-complete).