LU-1081 fid: define special FID for BFL

The sequence of LUSTRE_BFL_FID is in conflict with
FID_SEQ_OST_MDT1, so reserve a new sequence for this FID.

Also it defines a new FID sequence(FID_SEQ_SPECIAL) for
later special purpose.

Move some special dot_lustre oid to lustre_idl.h, so avoid
oid conflict in future.

Signed-off-by: Wang Di <di.wang@whamcloud.com>
Change-Id: I556b31c706cc04c610c909f83e59f0cb9a821535
Reviewed-on: http://review.whamcloud.com/2180
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>