DECORATE: added "$obsolete" special comment. When present, it marks the thing as obsolete. It will be detected by "Check obsolete thing" Map Analysis Mode check and will be marked in the Thing Properties Window and the Thing Info panel.
Map Analysis mode: added "Check obsolete things" check.
Updated documentation ("DECORATE keys" page).
Updated ZDoom_DECORATE.cfg.
Added: thing categories defined in Game Configurations can now be nested.
Changed, Thing Edit window: thing categories now use different icons.
Fixed: Thing Edit and Vertex edit windows had incorrect help links.
Fixed: Sound Propagation and Sound Environment modes had incorrect help links.
Documentation: updated "DECORATE keys" and "Things Settings" pages.
Visual mode, 3d floors: sloped 3d floors are now always rendered as opaque (just like in GZDoom).
Fixed a crash when creating a new unknown thing (introduced in r2324).
Documentation: updated "Action Argument Settings" and "DECORATE keys" pages.
DECORATE: added "//$ArgNEnum" special comment. It can be used to specify an enum to use with the argument.
Documentation: updated "Action Argument Settings" and "DECORATE keys" pages.
Game Configurations: updated things in ZDoom "Bridges" category to use argument types 23 and 24.
Documentation: added "Action Argument Settings" page, updated "Basic Settings", "Map Format Settings", "Linedefs Settings" and "Things Settings" pages in Configurations -> Game Configurations group.
Documentation: updated "DECORATE keys" page.
Removed "Sectors Brightness Mode" action, because the mode itself was removed long ago...
Documentation: updated "DECORATE keys", "Things Settings" and "Linedefs Settings" pages.
Fixed, Texture Browser, High-DPI: bottom panel of ImageSelectorControl had incorrect height when using DPI scaling.
Changed, SplitterControl, High-DPI: DPI scaling is now used when drawing expand/collapse area.
Documentation: fixed typos, filled "Compiling GZDoom Builder" page.
