@pos Without @line

In XMIR, each <o/> that has @pos attribute, must have @line attribute as well.

Incorrect:

<program>
  <objects>
    <o pos="3" name="foo"/>
  </objects>
</program>

Correct:

<program>
  <objects>
    <o line="2" pos="3" name="foo"/>
  </objects>
</program>