On the fsfs-format7 branch:  Since we need to reconstruct directory
contents during optimizing pack, data no longer gets read in a
linear fashon.  Therefore, caching becomes important.

* subversion/svnadmin/svnadmin.c
  (cmd_table): make 'pack' sub-command accept the '-M' parameter

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1446856 13f79535-47bb-0310-9956-ffa450edef68