The `hashfile` function has been moved to ODB, next to `git_odb_hash`.
Global state has been removed from the dirent call in `status.c`,
because global state is killing the rainforest and causing global
warming.
Add git_status_hashfile() to get blob's object id for a file without adding
it to the object database or needing a repository at all.
This functionality is similar to `git hash-object` without '-w'.
