Powerpoint writer: Use ph name and idx for getting layout shapes

Internal change: when we take shapes from the layout for title,
content, etc, we should use the attributes of the "ph" (placeholder)
tag -- idx and name. This is what powerpoint uses internally, and
therefore seems more dependable across reference-docs than using the
shape names, as we had previously done.

There should be no output changes as a result of this commit.

0 files changed, 0 insertions, 0 deletions