cleanup error tags v2

[Christoph Hellwig <hch@lst.de>]

Hi all,

while adding error injection to new code I'm writing I got really annoyed
with all the places error tags had to be added.  This series cleans the
error tags so that only the definition and one table have to be updated.
I've also cleaned up a lot of the surroundings while at it.

Changes since v1:
 - add a big fat comment and a idef/undef pair for the ERRTAGS magic

Diffstat:
 libxfs/xfs_ag_resv.c    |    7 -
 libxfs/xfs_alloc.c      |    5 -
 libxfs/xfs_attr_leaf.c  |    2 
 libxfs/xfs_bmap.c       |   17 +--
 libxfs/xfs_btree.c      |    2 
 libxfs/xfs_da_btree.c   |    2 
 libxfs/xfs_dir2.c       |    2 
 libxfs/xfs_errortag.h   |  106 +++++++++++++----------
 libxfs/xfs_exchmaps.c   |    4 
 libxfs/xfs_ialloc.c     |    2 
 libxfs/xfs_inode_buf.c  |    4 
 libxfs/xfs_inode_fork.c |    3 
 libxfs/xfs_metafile.c   |    2 
 libxfs/xfs_refcount.c   |    7 -
 libxfs/xfs_rmap.c       |    2 
 libxfs/xfs_rtbitmap.c   |    2 
 scrub/cow_repair.c      |    4 
 scrub/repair.c          |    2 
 xfs_attr_item.c         |    2 
 xfs_buf.c               |    4 
 xfs_error.c             |  216 ++++++------------------------------------------
 xfs_error.h             |   47 ++++------
 xfs_inode.c             |   28 ++----
 xfs_iomap.c             |    4 
 xfs_log.c               |    8 -
 xfs_trans_ail.c         |    2 
 26 files changed, 165 insertions(+), 321 deletions(-)