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.
We have a game that has actual ZH_CNA, ZH_TWN translations and also ships with the same file set that formed ZH_CNA in previous game versions, when there was no separate Traditional/Simplified variants and was only one 'Chinese'
The current Portuguese entry is Brazilian dialect, so modifying the
description and adding an entry for European Portuguese.
This is required to deal with bug Trac #10791.
