title: Removing a key binding
body: <p>How can I remove a (globally set) key binding? My emacs binds <code>set-mark-command</code> to <code>C-@</code>, <code>C-SPC</code>, and <code>M-SPC</code> by default, and I want to free <code>C-SPC</code> from it without assigning something else within emacs so that I can use that for a keyboard shortcut defined in the OS.</p>