Currently the API (classes & methods) has a mix of full-uppercase terms or first-uppercase terms when it comes to abbreviations like DOM, GUI, XML.

Usually Qt & KF API uses first-uppercase also for abbreviations, so KXMLGUI should be made consistent.

Cannot be done before KF6:

• virtual methods cannot be easily deprecated
• class names are used as strings in Qt's meta-object system, e.g. for string-based connetions or qobject_cast, so a name alias via "using" is too easy to use in incompatible ways.