- it is not NOTIFY_INVAL_DELETE, but just NOTIFY_DELETE as the kernel is
  notified of entry being deleted and there is no invalidation here.
  uapi/linux/fuse.h does not use "_INVAL_" for NOTIFY_DELETE neither.

- similarly for "notify store/retrieve" _INVAL_ is not appropriate and
  neither is used in uapi/linux/fuse.h . However since we took more
  explicit approach for "notify store/retrieve" naming (see bdca0e6a
  "Add support for store notify") let's also add _CACHE suffix for
  "notify store/retrieve" operation names for consistency and for being
  less ambiguous.

- for inode/entry invalidation operations, let's use _INVAL_ in internal
  _OP_NOTIFY_*, similarly to how it is used in corresponding NOTIFY_*
  constant. For example:

	_OP_NOTIFY_ENTRY -> _OP_NOTIFY_INVAL_ENTRY	(corresponds to NOTIFY_INVAL_ENTRY)