Perform a search through the docs of removed entities.

We're lucky to have the Ifc- prefix to our entity names. Let's use that so that we can find dangling entity name references that no longer exist, so for example on

FanPHistory http://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/Pset_FanPHistory.htm it says:

> IFC2X2-CHANGE Sound attribute deleted in IFC2x2 Pset Addendum: Use IfcSoundProperties instead.

**IfcSoundProperties** obviously is nowhere to be found. This may either hint at structural deficiencies or minor corrections needed in the docs.