Reasons include:
- easier to type
- might want postprocessor directives again sometime, and listdirectives
can then use the directive/* files for either
- that it's done as a preprocessor step is an internal detail (and not a
very accurate one, really :-)
* Plugins can add new directories to the search path with the add_underlay
function.
* Split out smiley underlay files into a separate underlay, so if the plugin
isn't used, the wiki isn't bloated with all those files.