todo:
* utf8
* check that partition supports it, especially in unit test
* docs, explain user_xattr, mount -o remount
* change to use section 2 calls instead of section 3
* buffer size, reuse buffer?
* symbolic link handling (O_NOFOLLOW on Mac OS X)
* Check it can be used with Perl 5.6.x
* Test setting attributes on directories, as suggested at Brum.pm
* Factor out common code from the tests
* Refactor the buffer allocation into a common function in ExtAttr.xs

* Remove dependency on libattr on Linux - just define ENOATTR -> ENODATA?
  (Feels a bit evil to do that.)

* Unite somehow with File::Attributes (which is for file systems
  without xattrs)?

* Document pre-reqs for test suite: Test::Distribution, Test::Pod::Coverage,
  Test::YAML::Meta. Include these in a .spec file that we can include
  with distro

* Disallow nuls in the attribute names. The list handling will break
  if we allow this. (Alternative is to make the portable listxattr follow
  the BSD API, where the separator is a length byte.)

* Support new extensible system attributes (and its API) on Solaris?
  See the PSARC referenced in the docs and its fgetattr, etc.
  implementation.

