bring b_io up to the lastest write caching code. fsx and rundbench 1 pass in a

bring b_io up to the lastest write caching code.  fsx and rundbench 1 pass in a
96M all-in-one UML.

- prepare_write is throttled by finding dirty pages on the super block's
  dirty inodes and writing them to the network
- commit_write marks the page dirty and updates i_size
- writepage blocks writing the page and other dirty pages to the network
- sort the pages within a obd_brw batch so that block allocation isn't hosed
  on the OST
- don't change s_dirty's position on the list during writeback, that seems to
  be the job of writepage's callers
- don't try and mess with page's list membership after obd_brw completes,
  filemap_fdata{sync,wait} take care of that
- put a hack in obdo_to_inode that tricks ll_file_size into preferring the
  local i_size when there are cached pages on the inode
- add license blurb and editor instructions
- get rid of the management of vm lru pages and liod thread, prepare_write
  throttling and kupdate serve the same task (hopefully)
- remove unused ll_flush_inode_pages
- throw in a OSC-side "count > 0" assert to match a similar OST assert that
  I couldn't reproduce
- writeback will try to batch PTL_MD_MAX_IOV pages on the wire