aggregate music credits into a single file (individual files can still be used to override. useful for .hwp etc.)
foreach(dir
Fonts
Forts
Graphics
Locale
Maps
Missions
Music
Names
Scripts
Sounds
Themes
misc
)
add_subdirectory(${dir})
endforeach(dir)
if(${GL2})
add_subdirectory(Shaders)
endif(${GL2})