Clean up underscores in function and variable names

Try to fix all places where we accidentally used foo_bar instead
of fooBar for function names, function parameters, and variables.

(Lucas Rocha pointed out one example.)

http://bugzilla.gnome.org/show_bug.cgi?id=581141

js/ui/overlay.js

@@ -922,7 +922,7 @@ Overlay.prototype = {
     },
 
     _deactivate : function() {
-        Main.hide_overlay();
+        Main.hideOverlay();
     }
 };