Remove mouse highlight

This was bugging me especially in org-agenda, but I don't see why I
should bother with it in any other case.

global.org

@@ -149,7 +149,8 @@
      (mouse-wheel-mode -1)
      (setq mouse-autoselect-window nil
            mouse-yank-at-point nil
-           focus-follows-mouse nil)
+           focus-follows-mouse nil
+           mouse-highlight nil)
    #+END_SRC
 *** TODO Find out what of the above is necessary given the disable-mouse mode below
     Use the ~disable-mouse~ package by Steve Purcell available at