Automatically fall back to LOGICAL_INO if LOGICAL_INO_V2 fails and no
_V2 flags are used.
Add methods to set the flags argument with build portability to older
headers.
Use thread_local storage for the somewhat large buffers used by
LOGICAL_INO_V2 (and other users of BtrfsDataContainer like INO_PATHS).
Signed-off-by: Zygo Blaxell <bees@furryterror.org>