On the fsfs-format7 branch: Minimize cache and index addressing.
Membuffer cache access is fastest for 16 byte-sized keys, so use
them where possible.

* subversion/libsvn_fs_fs/index.h
  (svn_fs_fs__page_cache_key): shorten revision values to 32 bits

* subversion/libsvn_fs_fs/fs.h
  (window_cache_key_t): ditto; reorder to allow struct packing

* subversion/libsvn_fs_fs/index.c
  (packed_stream_close): itself a shallow wrapper -> should be inlined
  (prefetch_l2p_pages,
   l2p_index_lookup,
   prefetch_p2l_page,
   get_p2l_keys): cast revs to 32 bits; assert() that that's o.k.

* subversion/libsvn_fs_fs/cached_data.c
  (get_window_key): ditto


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1481452 13f79535-47bb-0310-9956-ffa450edef68