Fix: [Win32] Original window size was lost when tabbing in and out of fullscreen.

src/video/win32_v.cpp

@@ -715,7 +715,9 @@ LRESULT CALLBACK WndProcGdi(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 			if (video_driver->fullscreen) {
 				if (active && minimized) {
 					/* Restore the game window */
+					Dimension d = _bck_resolution; // Save current non-fullscreen window size as it will be overwritten by ShowWindow.
 					ShowWindow(hwnd, SW_RESTORE);
+					_bck_resolution = d;
 					video_driver->MakeWindow(true);
 				} else if (!active && !minimized) {
 					/* Minimise the window and restore desktop */