Add ST_* constants to OsConstants

Expose ST_* constants via OsConstants. Without these constants being
exposed, it's impossible to meaningfully use StructStatVfs.f_flag
returned from the Os.statvfs() call.

For now, @hide the new constants.

Change-Id: I82536521972e9e87a1936dd712b9e8153d120cc1
2 files changed