Create a 1.5.x backport branch for the issue #3392 group.

Creating the branch from the 1.5.x-r36879 branch as that group must be
merged first to avoid conflicts in merge_tests.py.  The issue #3392 group
can be applied independently of the 36879 group and if this becomes necessary
I'll create a separate branch.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.5.x-issue3392@877170 13f79535-47bb-0310-9956-ffa450edef68