[PATCH] For 'svn patch', fix bug when reading patches without index lines

Hi!

I have my own branch, and I was told that I could just commit there. But
it's _scary_. I'll ask for permission first.

[[[
Fix bug with 'svn patch' not recognizing diff headers when parsing
patches without the 'Index' line and the '======' line. The old code
just assumed that the first line after the hunk would not be a '-'. But
it can be so we must handle it.

* subversion/libsvn_diff/parse-diff.c
  (parse_next_hunk): Check that we have not read all the lines, that the
    hunk header said, the hunk should consist of. We need to check for
    both nr of modified and original lines since we can do a reverse
    parsing. That means treating '+' as '-' and the other way around.

* subversion/tests/cmdline/patch_tests.py
  (patch_no_index_line): New.
  (test_list): Add the new test.
]]]