Reduce dynamic memory consumption and cache pressure when reading
directories and node properties.

The idea is that the actual directory or property object, respectively,
is the "fulltext" that will be cached.  There is little point in caching
the reconstructed intermediate fulltext.  So, let the callers of
get_contents() decide whether fulltexts may be cached.

* subversion/libsvn_fs_fs/cached_data.h
  (svn_fs_fs__get_contents): Add CACHE_FULLTEXT parameter.

* subversion/libsvn_fs_fs/cached_data.c
  (svn_fs_fs__get_contents): Skip cache lookup and prevent fulltext
                             caching of the item being read depending
                             on the CACHE_FULLTEXT parameter value.
  (svn_fs_fs__get_file_delta_stream): We allow fulltext caching for files.
  (get_dir_contents,
   svn_fs_fs__get_proplist): We don't for dirs and properties.

* subversion/libsvn_fs_fs/dag.c
  (svn_fs_fs__dag_get_contents): We allow fulltext caching for files.

* subversion/libsvn_fs_fs/transaction.c
  (rep_write_get_baton): Ditto.
  (write_container_delta_rep): We disable fulltext caching for dirs & props.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1565100 13f79535-47bb-0310-9956-ffa450edef68