xfs: Changes for 4.6-rc1

Change summary:
o error propagation for direct IO failures fixes for both XFS and ext4
o new quota interfaces and XFS implementation for iterating all the quota IDs
  in the filesystem
o locking fixes for real-time device extent allocation
o reduction of duplicate information in the xfs and vfs inode, saving roughly
  100 bytes of memory per cached inode.
o buffer flag cleanup
o rework of the writepage code to use the generic write clustering mechanisms
o several fixes for inode flag based DAX enablement
o rework of remount option parsing
o compile time verification of on-disk format structure sizes
o delayed allocation reservation overrun fixes
o lots of little error handling fixes
o small memory leak fixes
o enable xfsaild freezing again
Merge branch 'xfs-misc-fixes-4.6-4' into for-next