WIP: remove the old database abstraction layer

remove such classes:
- DbBase
- DbConn
- DbTextStream
- Db

while here:
- remove: TextStream, SLog, TexTextStream

winixd/core/winixrequest.h

@@ -5,7 +5,7 @@
  */
 
 /*
- * Copyright (c) 2018, Tomasz Sowa
+ * Copyright (c) 2018-2024, Tomasz Sowa
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -38,7 +38,6 @@
 #include "core/winixsystem.h"
 #include "core/cur.h"
 #include "core/sessionmanager.h"
-#include "core/slog.h"
 #include "templates/locale.h"
 
 
@@ -66,8 +65,6 @@ public:
 
 protected:
 
-	SLog slog;
-
 	Cur * cur;
 	Locale * locale; // locales can be used not only in templates -- should be moved to a better place
 	SessionManager * session_manager; // may it should be moved to WinixSystem or System?