GameControl: don't leak effects

coverity 4437 4438
GameScript: don't leak effects

coverity 4441 4442 4443 4444
PutMapNotes: pst coordinates are stored as dwords, so don't cast one to a word
AREImporter::PutMapnotes: according to iesdp, pst color is a dword

coverity 4493 - don't write garbage
GameScript::UsedExit: removed logically dead code

coverity 4343
GameScript::StartMusic: removed potential out-of-bounds access

coverity 4418
Game::GetXPFromCR: avoid unlikely div-by-0

coverity 4347