HasSetting from 3dfa23cd25 is actually redundant with
IGUIObject::SettingExists.
GetSettingPointer from 8f4f8e240f is superseded by GetSetting reference
following 3dfa23cd25 and 040624acff.
Deregister copying SetSetting variants for CStr and CStrW following copy
removal in 040624acff.
The default template <typename T=int> from c2a71e41bf can be removed
following FallBackSprite/FallBackColor removal in 9985fcf5bd and
RecurseObject unification in d4d5187c9d.
Delete all unused GUI includes, refs D1478.
Remove GUIUtil friend class following something.
Differential Revision: https://code.wildfiregames.com/D2225
Tested on: gcc 9.1.0, Jenkins
This was SVN commit r22779.