Start work on making xbanan portable

This will allow usage of xbanan on non banan-os platforms. I added a
"native" SDL2 port so it can be used without the window manager

xbanan/Events.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "Types.h"
+
+void register_event_fd(int fd, void* data);
+void unregister_event_fd(int fd);
+
+void on_window_close_event(WINDOW wid);
+void on_window_resize_event(WINDOW wid, uint32_t width, uint32_t height);
+void on_window_focus_event(WINDOW wid, bool focused);
+void on_window_fullscreen_event(WINDOW wid, bool is_fullscreen);
+
+void on_mouse_move_event(WINDOW wid, int32_t x, int32_t y);
+void on_mouse_button_event(WINDOW wid, uint8_t xbutton, bool pressed);
+void on_key_event(WINDOW wid, uint8_t scancode, uint8_t xmod, bool pressed);