Mac: Don't quit Emacs when window is closed

[Luis Gerhorst]

Hi,
I have the problem that I always quit Emacs by mistake when I am done with a 
task by clicking the button to close the Emacs window. I have a few ideas / 
questions:

- Wouldn't it be a good idea to make Emacs act like most Mac application and 
not quit the application when the window is closed? Is there some reason why 
this is not possible?
- How can I disable the button to close the window or make it call 
suspend-frame instead of save-buffers-kill-emacs?

Best wishes from Germany,
Luis Gerhorst