Replace TSMDBGrid in Data + Query tabs by TTntDBGrid.

- Implement an alternative solution for handling sorted columns without usage of SMDBGrid's sortcolumns. Move relevant structures and functions from data_sorting.pas to childwin.pas and use them in both units.
- Upgrade some code parts to use WideStrings instead of Strings so they don't break with the new grid.
- Use Grid.OnDrawDataCell as an alternative to Grid.OnGetCellParams as the latter one is a feature of SMDBGrid
- Cosmetic: enhance screen real estate in viewdata()

source/main.pas

@@ -15,8 +15,8 @@ uses
   Windows, SysUtils, Classes, Graphics, Forms, Controls, Menus,
   StdCtrls, Dialogs, Buttons, Messages, ExtCtrls, ComCtrls, StdActns,
   ActnList, ImgList, Registry, ShellApi, ToolWin, Clipbrd, db, DBCtrls,
-  SynMemo, synedit, SynEditTypes, smdbgrid, ZDataSet, ZSqlProcessor,
-  HeidiComp, sqlhelp, MysqlQueryThread, Childwin, VirtualTrees;
+  SynMemo, synedit, SynEditTypes, ZDataSet, ZSqlProcessor,
+  HeidiComp, sqlhelp, MysqlQueryThread, Childwin, VirtualTrees, TntDBGrids;
 
 type
   TMainForm = class(TForm)
@@ -898,7 +898,7 @@ end;
 // view HTML
 procedure TMainForm.HTMLviewExecute(Sender: TObject);
 var
-  g              : TSMDBGrid;
+  g              : TTntDBGrid;
   filename,extension   : String;
   f              : Textfile;
   buffer         : array[0..MAX_PATH] of char;