Implement the full 'svn:*' property validation and conicalization for 'svnmucc'
in the mtcc api.

* subversion/libsvn_client/mtcc.c
  (get_origin): If a node is added and has no recorded origin, report the
    node as without origin.
  (mtcc_prop_get_baton): New struct.
  (mtcc_prop_getter): New function.
  (svn_client_mtcc_add_propset): Use the result of svn_subst_translate_string2
    instead of ignoring it. Call svn_wc_canonicalize_svn_prop() for further
    canonicalizations and verifications.

* subversion/tests/libsvn_client/mtcc-test.c
  (includes): Add svn_props.h.
  (test_propset): Extend testcase with some explicit failure cases.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1551085 13f79535-47bb-0310-9956-ffa450edef68