Merge revisions 1511324,-46,-63,-64,1532410,1535668 from the "log
addressing" branch into /trunk and resolved trivial text conflicts.

These patches introduce the svn_fs__compatible_version() API and
use it where appropriate.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1546697 13f79535-47bb-0310-9956-ffa450edef68