whois: add lookahead mode for the timetable entry after the next stop

Dispatcher scripts that route trains at a station based on where they
go afterwards (e.g. a big terminal throat with several outbound
directions) have no way to read that: whois +40 only exposes the
current/next timetable entry (NextStop()/IsStop()), which while the
train is at that very station is that station itself.

Adds flags::whois_ahead (bit 6, previously unused) plus
TTrainParameters::StationNameAhead(Offset)/StationIsStopAhead(Offset),
returning the raw TimeTable[] entry Offset positions past StationIndex
(name and whether it's a booked stop, "none"/false past the end of the
timetable). The new whois branch calls both with Offset=1, mirroring
the existing +40 branch's UpdateValues()/WriteLog() shape.

Logic-verified with an isolated harness mirroring the touched types
(TTrainParameters/TController/TMemCell shapes and the exact function
bodies); not yet build-tested against the full engine locally - relying
on CI for that.

world/mtable.cpp

@@ -77,6 +77,22 @@ bool TTrainParameters::IsLastStop() const {
     return StationIndex >= StationCount;
 }
 
+std::string TTrainParameters::StationNameAhead( int Offset ) const
+{ // nazwa wpisu rozkladu Offset pozycji za aktualnym (bez pomijania przelotow)
+    int const idx { StationIndex + Offset };
+    if( ( idx < 1 ) || ( idx > StationCount ) )
+        return "none";
+    return TimeTable[idx].StationName;
+}
+
+bool TTrainParameters::StationIsStopAhead( int Offset ) const
+{ // czy wpis Offset pozycji za aktualnym to zaplanowany postoj
+    int const idx { StationIndex + Offset };
+    if( ( idx < 1 ) || ( idx > StationCount ) )
+        return false;
+    return TimeTable[idx].Ah >= 0; //-1 to brak postoju
+}
+
 
 bool TTrainParameters::IsMaintenance() const {
     if( StationIndex <= StationCount )