[cppcheck] Remove unused ARX_FOGS_KillByIndex()
[cppcheck] Remove unused EERIEPrecalcLights()
Remove unused EERIE_LIGHT_Apply()
Remove unused ARX_EERIE_LIGHT_Make()
Remove unused my_CheckInPoly()
[cppcheck] Remove unused ReloadScript()
[cppcheck] Remove unused audio::getMixerVolume()
Remove CalcFPS()::fFPS

Was never read.
[cppcheck] Fix bogus bitwise AND
Remove redundant SHOW_FLAG_IN_INVENTORY change
[cppcheck] Remove redundant NULL check
[cppcheck] Remove redundant if condition
[cppcheck] Remove dead break after goto
[cppcheck] Remove unread variable
[cppcheck] Remove unread variable
[cppcheck] Remove redundant NULL check
[cppcheck] Remove unused struct OBJFX
[cppcheck] Remove unread variable assignment
[cppcheck] Remove unread local variable
[cppcheck] Remove duplicated flag