Revision 1497002

When possible pass the stream's file to external diff rather than
creating a temporary spool file.  Fixes issue 4382.

* subversion/include/private/svn_io_private.h
  (svn_stream__aprfile): New.

* subversion/libsvn_subr/stream.c
  (struct svn_stream_t): Add file member.
  (svn_stream_create, svn_stream_from_aprfile2): Set file member.
  (svn_stream__aprfile): New.

* subversion/libsvn_client/diff.c
  (diff_content_changed): Use stream's file if possible.

* subversion/svnlook/svnlook.c
  (print_diff_tree): Use stream's file if possible.