Previously, for an XML like this:
the call like
int pos = getXPathPosition(pDoc, "/x:sharedItems", "absent");
gave 3. That could result in mistakes, when a test would assert
on position "3" for a child element which name is mistyped.
I made such a mistake when creating a unit test trying to assert on
a position of the last element, and writing its name as "x:m", like
in rXPath itself; the return was 3, and I initially wrongly assumed
that the return is 1-based (like in xpath bracketed expressions).
rChildName made const OString&, for consistency with rXPath, or with
rAttribute in getXPath: child name is just a part of a longer xpath.
Reviewed-by: Mike Kaganski <firstname.lastname@example.org>