On the fsfs-format7 branch:  Make l2p index headers to more suitable to caching. 

* subversion/libsvn_fs_fs/index.c
  (l2p_index_header_t): switch revision page indexes from pointers to indexes
   get_l2p_header,
   l2p_index_lookup,
   svn_fs_fs__l2p_get_max_ids): update access code

* subversion/libsvn_fs_fs/index.h
  (svn_fs_fs__p2l_index_create): clarify docstring

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1443805 13f79535-47bb-0310-9956-ffa450edef68