Merge branch 'refs/heads/t/attribute_fix'

Merge branch 'refs/heads/t/attribute_fix'

com_setatt() was broken if more than 32 attributes are defined. The
branch merged in this commit contains a fix for this bug, and a new
test that exercises the code related to attributes.

Was cooking in next for six weeks.

* refs/heads/t/attribute_fix:
  manual: Add realpath to list of packages.
  Add test that exercises attribute code.
  test-lib: Canonicalize test_dir.
  attribute: Avoid shifting 32 bit integers.