This is currently only (partially) implemented for the 16-color Mac
versions of Loom and Indiana Jones and the Last Crusade. The text is
still drawn in color, since that's rendered separately, but I'm
committing this now while it still works.
Adding @defgroup and @ingroup doxygen tags into all headers
in the common folder that contain doxygen blocks.
This improves the structure, readability, and findability
of information in the resulting output.
This commit targets purely structure and does not deal with
the content of the currently existing doxygen documentation.
