Sync FSX with FSFS.  Merge r1640061 from FSFS and resolve the usual
naming and text conflicts.

This ports the 'svnadmin verify --metadata-only' improvements to FSX.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1645584 13f79535-47bb-0310-9956-ffa450edef68