.pptx was introduced in PowerPoint 2007.
Remove "(added previously)".
Rephrase AddAnimationButtonSupertip.
ZoomIn/ZoomOutButton: "Adds a slide with animations" -> "Creates an animation slide."
Comment pointing out typo in constant name.
Rephrase to remove mentions of user ("you").
Click on this button -> Click this button.
Rephase MoveCropShapeButtonSupertip.
Remove "on the fly."
Rephrase AddSpotlightButtonSupertip.
Rephrase ReloadSpotlightButtonSupertip.
Rephrase AddAudioButtonSupertip.
"and click this" -> "then click this"
More concise AddAudioButtonSupertip.
Change GenerateAudioButton to match AddAudioButton.
Cut length of narrate/caption supertips.
Rephrase highlight supertips.
Rephrase VersionNotCompatible message.

Removes the mention of specific versions to emphasise that the
file's format is the problem.
Concise message for online presentations.
Rephrase ShapeCorruptedError.