Add more default variables
Add more default variables

- flag
- sort_algo
- clang_complete_database

Signed-off-by: Koichi Shiraishi <13fbd79c3d390e5d6585a21e11ff5ec1970cff0c@zchee.io>

zchee/deoplete-clang,zchee/deoplete-clang,zchee/deoplete-clang