todo:
utf8
warnings
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
for "operation not supported" note must be prefixed with "user"
buffer size, reuse buffer?
throw exceptions rather than warnings on getxattr() failure
symbolic link handling
Check it can be used with Perl 5.6.x
Factor out common code from the tests
Refactor the buffer allocation into a common function in ExtAttr.xs
Write tests for testing creation/replacement of attributes (and failure cases)
