added a gameflag for the slight difference in continuation handling

fixes bg2 spectral and spirit trolls immortality after the how djinni change
fx_play_visual_effect: check for null target earlier (potential crash)

coverity 4464
MapControl::OnMouseDown: make doubleclicking possible

coverity 4340
Actor::PlayHitSound: moved the armor check safety, so it's not dead code

coverity 4345
GameScript::SetPlayerSound: avoid out-of-bounds write

coverity 4419
GameScript::SetMusic: avoid out-of-bounds write

coverity 4420