Find a xOpt in the list of xOpts in pIxOpts matching nOptId. There may be multiple matches (either in the case of a multi-valued xOpt, or in the case of overrides). In this case nIndex specifies how far into the list of xOpts that match nOptId to look. pItem is filled in with the matching xOpt contents. nIndex is zero-based.
- pIxOpts:the interface pointer.
- nOptId:id of the option to find in the options list, XOPT_ANY returns the nIndexth option, if there is one...
- nIndex:which (if there are multiple xOpts of the same id) to get nIndex counts from most recently AddOpt()ed option, it's zero-based.
- pItem:where to stick the found xOpt
int IxOpts_GetOpt(IxOpts *pIxOpts, int32 nOptId, int32 nIndex, xOpt *pItem)