Fix issue #3702 'Unable to perform case-only rename on windows' by adding a new flag to svn_client_args_to_target_array (revving it in the process), so it can perform specialized case-canonicalization behavior for supporting case-only renames.
* subversion/tests/cmdline/copy_tests.py (case_only_rename): Remove XFail marker. Fix issue description according to the changed summary of issue #3702.
* subversion/include/svn_client.h (svn_client_args_to_target_array): Deprecate, succeeded by ... (svn_client_args_to_target_array2): ... new function, carrying a new argument KEEP_LAST_ORIGPATH_ON_TRUEPATH_COLLISION.
* subversion/libsvn_client/cmdline.c (svn_client_args_to_target_array2): Make use of new flag KEEP_LAST_ORIGPATH_ON_TRUEPATH_COLLISION to undo truepath-conversion of the last of 2 targets if they both have the same 'truepath'.