Properly calculate subdirectory filesystem paths for file:/// urls where the
root of the repository points to the root of a Windows drive root.
(Resolves an of by one error for this specific case)

* subversion/libsvn_ra_local/split_url.c
  (svn_ra_local__split_URL): Fix 'clever' code that didn't cover a specific
    Windows corner case.

* subversion/tests/cmdline/checkout_tests.py
  (checkout_wc_from_drive): Extend testcase to cover two variants of this
    issue.

Found by: Andy Levy <andy.levy{_AT_}gmail.com>


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1518184 13f79535-47bb-0310-9956-ffa450edef68