Display last system error when plink process could not be started for…

… some reason. Helps in debugging. See https://www.heidisql.com/forum.php?t=34556#p35000

source/dbconnection.pas

@@ -871,7 +871,9 @@ procedure TPlink.Connect;
        PChar(GetCurrentDir),
        StartupInfo,
        FProcessInfo) then begin
-    raise EDbError.CreateFmt(_('Could not execute PLink: %s'), [CRLF+PlinkCmdDisplay]);
+    ErrorText := CRLF + CRLF + PlinkCmdDisplay + CRLF + CRLF + 'System message: ' + SysErrorMessage(GetLastError);
+    ErrorText := f_('Could not execute PLink: %s', [ErrorText]);
+    raise EDbError.Create(ErrorText);
   end;
 
   // Wait until timeout has finished, or some text returned.