The code for the engine options dialog for AGS was emoved from
detection.cpp to its own file a while back but we forgot to update
the POTFILES, so that dialog was no longer translated.
Also remove an include for translation.h in detection.cpp as it is
no longer needed.
For unknown variants it now checks that the file is actually an
AGS game to avoid false positive due to generic names used by
some of the detection entries (such as 'game.exe'). Also unknown
variants can now be added.
AGS games can have multiple languages by providing
additional translations as .tra files. The language
selection is done by setting the config "translation"
key to the tra file name. This means that we cannot
easily use the standard ScummVM language selection
for this purpose as the tra file name may not map
to language names easily.
The approach in this commit does something similar
to the original games by detecting at runtime the
available tra files.
