Xar update

[dmacks]

New libversion on a fork that was abandoned more recently than the original (Issue #20), with switch to openssl300 (Issue #499)

[nieder]

Lots of test failures (8 total) like this:

FAILED: zero_length_default_compression
Traceback (most recent call last):
  File "data.py", line 95, in <module>
    case("{f}.xar".format(f=case.func_name))
  File "data.py", line 45, in zero_length_default_compression
    _zero_length(filename)
  File "data.py", line 37, in _zero_length
    util.touch(os.path.join(directory, "empty"))
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 24, in __exit__
    self.gen.next()
  File "data.py", line 25, in _data_test
    util.assert_identical_directories(directory, os.path.join(extracted, "data_scratch"))
  File "/sw/build.build/libxar-apple1-shlibs-494.81.1-1/xar-xar-494.81.1/xar/test/util.py", line 125, in assert_identical_directories
    assert stat1.st_mtime == stat2.st_mtime, "mtime mismatch for \"{e1}\" and \"{e2}\"".format(e1=entry1, e2=entry2)
AssertionError: mtime mismatch for "/sw/build.build/libxar-apple1-shlibs-494.81.1-1/xar-xar-494.81.1/xar/test/data_scratch/empty" and "/sw/build.build/libxar-apple1-shlibs-494.81.1-1/xar-xar-494.81.1/xar/test/data_extracted/data_scratch/empty"