Speed up serialization of DAG and noderev structures for our caches.
Turns out that 503 bytes is often not sufficient for noderevs with
longer path names and even less so for DAG nodes.  Up that to 1007
bytes (+1 0-terminator +16 bytes memory management overhead = 1kB).

* subversion/libsvn_fs_fs/dag.c
  (svn_fs_fs__dag_serialize): bump default buffer size

* subversion/libsvn_fs_fs/temp_serializer.c
  (svn_fs_fs__serialize_node_revision): ditto

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1442071 13f79535-47bb-0310-9956-ffa450edef68