Improves RT window position management, fixes #6233 (#6239)

* Improves RT window events detection and RT window position computation

* Fixes some limitations in specific cases for Windows and MacOS

* Fixes RT window not restoring saved position at startup

- When maximized at startup, RT window position wasn't restored from
options file. So when unmaximazing RT, position was set to up left
corner instead of restored one
- Other fix: Removed some uses of deprecated Gtk functions

* Improves RT window management for independant edit window mode

Other fixes:
- Monitor ID wasn't correctly computed
- Removes some other deprecated functions uses
- Removes debug printf

* Fixes editor window aspects not restored in MEOW mode on Linux

Other fixes:
- Removes some Gtk warnings when adding a new editor panel in MEOW mode
- Adds robustness to avoid RT windows outside screen at startup loading
corrupted options file with negative position values

* Fixes incorrect max position saturation in dual screen configurations

rtgui/rtwindow.h

@@ -51,6 +51,8 @@ private:
     Gtk::ProgressBar prProgBar;
     PLDBridge* pldBridge;
     bool is_fullscreen;
+    bool is_minimized;
+    sigc::connection onConfEventConn;
     bool on_delete_has_run;
     Gtk::Button * btn_fullscreen;
 
@@ -96,6 +98,7 @@ public:
     void showPreferences ();
     void on_realize () override;
     void toggle_fullscreen ();
+    void get_position(int& x, int& y) const;
 
     void setProgress(double p) override;
     void setProgressStr(const Glib::ustring& str) override;