TAKE - make xfs superblock coherent with block layer

[Steve Lord <lord@sgi.com>]

The xfs super block lived in its own special buffer which was
invisible from the /dev/xxx interface. This makes it a general
purpose buffer. No change in filesystem functionality, but now
I understand why the locking on this beast needs work.

Date:  Wed Feb 27 13:15:13 PST 2002
Workarea:  jen.americas.sgi.com:/src/lord/xfs-merge.2.4

The following file(s) were checked into:
  bonnie.engr.sgi.com:/isms/slinx/2.4.x-xfs


Modid:  2.4.x-xfs:slinx:112914a
linux/fs/xfs/xfs_buf.h - 1.81
	- Make XFS_BUF_V_IODONESEMA do something - forced shutdown only case

linux/fs/xfs/xfs_log_recover.c - 1.219
	- minor cleanup

linux/fs/xfs/xfs_mount.c - 1.270
	- Change how we manage the super block buffer - it is now in the 
	  cache with all the other metadata

linux/fs/xfs/pagebuf/page_buf_locking.c - 1.5
	- Fold some code together, we were doing everything pagebuf_lock does,
	  but not calling it.

linux/fs/xfs/pagebuf/page_buf.c - 1.9
	- Expand pagebuf_rele for the PBF_FS_MANAGED flag - the filesystem does not
	  want this buffer to get freed.

linux/fs/xfs/pagebuf/page_buf.h - 1.5
	- Define PBF_FS_MANAGED