On the fsfs-format7 branch: Tune the changed path list packing code
to try harder to put as many lists into a single container as possible.

Due to the awesome compression ratios of 1:100 for certain patterns,
we significantly over-estimated the on-disk size of the container.
Now, we will serialize the container when we might have hit the block
size limit and see how much space will *actually* be left.

* subversion/libsvn_fs_fs/changes.c
  (svn_fs_fs__changes_estimate_size): 

* subversion/libsvn_fs_fs/caching.c
  (dump_cache_statistics): give a tighter estimate (still grossly over-
                           estimating in most cases)


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1481458 13f79535-47bb-0310-9956-ffa450edef68