add check for g_lastHidden to player_spawn

* this prevents the last hidden being viewed as a spy, and forced to solly
* g_lastHiddenClassCorrected ensures the last hidden only gets forced to their pre-hidden
  class onces
* everytime SelectHidden is called (round start->timer new game->NewGame->SelectHidden())
  g_lastHiddenClassCorrected is set to false for the last hidden's first spawn