SendTriggerToAll: also send to area itself

Fixes Vithal not appearing in AR2100 when Freedom spell is cast
(BG2).
yet more robustness when faced with broken dialog scripts

Also handle the mergestrings case properly when an argument is not
terminated with quotes. Fixes udvith.dlg in BG2.
add new flag to check for unscheduled actors in ValidTarget

It turns out unscheduled actors can be targeted after all, e.g. for
the Activate() script action.