made windowed-mode windows be resize-able/scale-able - guest OS display size is retained, though

BasiliskII/src/SDL/video_sdl.cpp

diff --git a/BasiliskII/src/SDL/video_sdl.cpp b/BasiliskII/src/SDL/video_sdl.cpp
index 45e06da..c2356ce 100755
--- a/BasiliskII/src/SDL/video_sdl.cpp
+++ b/BasiliskII/src/SDL/video_sdl.cpp
@@ -703,6 +703,8 @@
 		window_flags |= SDL_WINDOW_FULLSCREEN_DESKTOP;
 		window_width = desktop_mode.w;
 		window_height = desktop_mode.h;
+	} else {
+		window_flags |= SDL_WINDOW_RESIZABLE;
 	}
 	
 	if (sdl_window) {