Codechange: Add base() method to StrongType to allow access to the base type without casting. (#11445)

This removes the ability to explicitly cast to the base type, but the requirement
to use .base() means the conversion is still explicit.

src/script/api/script_basestation.cpp

@@ -63,5 +63,5 @@
 {
 	if (!IsValidBaseStation(station_id)) return ScriptDate::DATE_INVALID;
 
-	return (ScriptDate::Date)(int32_t)::BaseStation::Get(station_id)->build_date;
+	return (ScriptDate::Date)::BaseStation::Get(station_id)->build_date.base();
 }