Tests that accessing XPath namespace axis doesn't cause a crash, see bug 12724.

The actual results are incorrect, because XPath namespace nodes are not implemented yet.

FAILURE: 0 result nodes (should be 7)
FAILURE: 0 result nodes (should be 7)
FAILURE: 0 result nodes (should be 7)
FAILURE: 0 result nodes (should be 6)
FAILURE: 0 result nodes (should be 7)
PASS: 4 result nodes