bypass real → integer conversion → real promotion in dateUtils.dateOf

The `dateUtils.dateOf` function takes one `tDateTime` value, a `real` value,
converts it to an `integer` using `trunc`, and then the value is automatically
promoted to a `real` value again (because of result data type `tDateTime`).

This is unnecessary (unless an error is the desired behavior).
You can use just `system.int` to obtain the integral (= date) part of `tDateTime`.

packages/rtl-objpas/src/inc/dateutil.inc

@@ -622,7 +622,7 @@ end;
 
 Function DateOf(const AValue: TDateTime): TDateTime; inline;
 begin
-  Result:=Trunc(AValue);
+  Result:=Int(AValue);
 end;