[Bf-committers] Menu bar riffing behaviour (open subsequent menus on hover)

[Matthew Reid]

Hi all

I'd like to contribute my first piece of functionality for blender. I've
changed the menu bar behaviour to open the first menu on click, and
subsequent menus on hover. This is also known as menu riffing, and matches
the default menu behaviour of Windows and OSX applications.

Here's a video:
https://vimeo.com/97717874

I'd like to make this a user configurable option if people think it will be
useful.

-Matthew